Should I use wa, ga or o?

This question appeared in a test I recently took in my Nihongo class:

Fuutou ( ) kami de tsukurimasu.
Make envelopes with papar.

and

Taiya ( ) gomu de tsukurimasu.
Make tires with rubber.

In both questions, I entered ''ga'' in the blank and was marked as incorrect. The sensei said the correct answer should be ''wa''. After reflection and going over some grammar texts, I still find it hard to accept that ''wa'' is the correct answer and in fact I believe ''o'' is the actual correct answer. I asked the sensei about this and he still maintains it is ''wa'' but I cannot understand this.

Anyone help?

I think the original English sentence might have a bit of a problem.
If the English sentence went:
�gEnvelopes are made with paper�h and �gTires are made with rubber,�h meaning general statements, then the correct answer/natural choice in both cases will be �gwa,�h because �gfuutou�h and �gtaiya�h are just the topics of the respective sentence.
(The Japanese answer then could have been "Fuuto wa kami de dekiteimasu.")

If the focus is on the action, meaning,
�g(In our factory) we make envelopes from paper�h or �gMake envelopes from paper (imperative),�h �g(In my job) I make tires from rubber�h or �gMake tires from rubber (imperative)�h then the more natural choice will be to consider �gfuuto�h and �gtaiya�h as the direct object of the action, thus the choice will be �go�h as you say.

(In both cases, as you must have come to understand, �gga�h would not be the appropriate choice, as this would make �gfuuto�h and �gtaiya�h the subject of the sentence, which they are not.)

The teacher should have allowed your choice of �go�h as OK, while, I admit, if the intention of that section of the test was only to test you on the distinction between �gwa�h and �gga,�h the teacher might not allow that.

I hope this helps at least a bit...

I also think these are very bad example sentences, which are guaranteed to confuse learners.

AK san is right.

How to use wa, ga, or o is depend on who make those envelopes.

Fuutou wa kami de tsukurimasu.
= Envelopes are made with paper in a factory(or somewhere else)
This sentense should be
"Fuutou wa kami kara tsukuraremasu."

Fuutou ga kami de tsukurimasu.
=Mr Fuutou makes something with paper.(laugh)

Fuutou wo kami de tsukurimasu.
= I make envelopes with paper.
This sentense should be
"Watasi wa fuutou wo kami de tsukurimasu."

Thanks for reading

Thanks for all your responses which are very helpful.
But first, I must apologize because I realize that I did not make my question very clear.
In the test, there was no English. The English part is just my guess at what the translation should be. The test only asked for the filling in the blank space.

So from your answers, I guess this means that "o" should be the correct answer and that "wa" is unacceptable because it will mean that "Mr Envelope" makes something with paper.

Yes, after I sent in my post, I was actually wondering if you had the English sentences in the test. So you were to just fill in the blank with the correct word, without any English sentence.

The answers can be �go�h or �gwa,�h but NEVER �gga.�h (If you use �gga,�h then you�fve got �gMr. Envelope.�h)

If you use �gwa,�h both sentences will be very simply general statements about what envelopes are made of, or what people make envelopes out of, without any emphasis. Just plain statements describing paper and tires.

If you use �go,�h then the emphasis will be on WHAT you make out of paper/rubber, rather than general statements. So:
- What do you make of paper? (�gKami de nani o tsukurimasuka?)
- We make envelopes out of paper (�gFuuto o (kami de) tsukurimasu.�h)

So I�fd say, without the English, �go�h and �gwa�h can be correct. It's more the context that determines whether "o" or "wa" will be used. Sorry if I used some grammar vocabulary earlier in my explanation; I just hope that your teacher can provide good explanation for you why he says no to "o"!

More thanks to AK for your further elaboration. This is very interesting for me.

Actually I thought that "o" is the appropriate answer because as Misa put it, the correct sentence will be:
Watashi wa fuutou wo kami de tsukurimasu.
Except the first part "watashi wa" is omitted. This can be in the context of something like an answer to: "nani o suru"?

On the other hand, I thought that even "wa" is not so appropriate since tsukuru is a transitive verb so it needs to have an object followed by an object maker "o". If the emphasis is on WHAT envelopes are made of then again, Misa's amendment seems more appropriate, using the passive voice of tsukurimasu:
Fuutou wa kami kara tsukuraremasu.

This is just what I think. I am just a beginner with about 80 hours of instruction in Japanese so far and hoping to do the Level 4 this year.

I came across this in romanji in an oral drill CD Rom:
Koko ni eigo o hanaseru hito wa imasu ka.

I don't understand why "ga" is not used instead of "wa" in this example.

(A)
- Heya ni tsukue wa arimasu ka.
- Hai, arimasu/Iie, arimasen.

(B)
- Heya ni nani ga arimasu ka.
- Teeburu ga arimasu.

"ga" is normally used to highlight the noun it follows.

What's the most important thing you want to know in the first question (A)? It is WHETHER a desk IS THERE OR NOT. Normally when you are asking if something/someone is there, you already are referring to that SOMETHING/SOMEONE (= you have a topic), and you are asking something about that topic: then you use "topic marker" = "wa."

In contrast, in (B), when you are asking WHAT is there (you don't know what it is), the most important thing you want to know is WHAT. In this case, since it is the WHAT part that matters, you use "ga," the "subject marker."

And the sentence you are asking about, "is there anyone who can speak English here?" the pattern is that of (A).

Ummm, see how this sits with you?? I may be a bit tired now to write out a decent answer but just wanted to give it a try... :)

In Japanese, wa is right.
We do not say Fuutou ga kami de tsukurimasu, nor Fuutou o kami de tsukurimasu.

In Japanese ga is offten omited but if you want to be correct O is more polite. But I dont know, it depends on the context of the sentence and who your talking to and where.