We "are going" to the expensive restaurant if Dad comes home.　

We 　　　 to the expensive restaurant if Dad comes home.　
(Ａ) go (Ｂ) will go (Ｃ) went (Ｄ) are going
The answer to the above question is option B.
Is option D also acceptable to native speakers?

It's possible in casual speech.

Option D is how you might inform someone of a decision you've made earlier.
Option B sounds like you've just made the decision and are informing others what it is.

In very casual speech you may also hear option A, as a shortened form of option B.

Only C is ungrammatical. A poor question, apparently.

Who wrote this question? Where did you see it?

jutfrank said:

Only C is ungrammatical. A poor question, apparently.

Who wrote this question? Where did you see it?

Click to expand...

It was designed by a Taiwanese teacher of English. I saw the question on a practice test paper.

We won't take a trip to Green Island if it ____ tomorrow morning.
(A) rained (B) rains (C) will rain (D) is raining
The answer to the above question is option B.
Is option D also acceptable to native speakers?

Yes, it is.

Is this written by the same Taiwanese teacher of English? What does this teacher believe is being practised exactly?

@sitifan I consider D less likely but not wrong.

Were these questions written by your English teacher?

sitifan said:

We won't take a trip to Green Island if it ____ tomorrow morning.
(A) rained (B) rains (C) will rain (D) is raining

Click to expand...

Option D isn't as likely here as in your first question.

jutfrank said:

Is this written by the same Taiwanese teacher of English? What does this teacher believe is being practised exactly?

Click to expand...

I don't know if it is written by the same person. Nor do I know what is being practiced.

emsr2d2 said:

Were these questions written by your English teacher?

Click to expand...

No. They are quoted from a practice test paper, provided by a publishing company in Taiwan.

Do you use this material in your lessons?

jutfrank said:

Do you use this material in your lessons?

Click to expand...

Yes.

Have you thought about not using it?

Can you tell us a little about your teaching context?

jutfrank said:

Have you thought about not using it?

Can you tell us a little about your teaching context?

Click to expand...

Yes, but many other teachers are still using it. I teach English at a junior high school.

Tarheel said:

@sitifan I consider D less likely but not wrong.

Click to expand...

Barque said:

Option D isn't as likely here as in your first question.

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I don't agree.

@sitifan If I was going to prepare multiple choice options for an exam I would make sure only one of them was correct.