What are you doing/going-to-do this evening?

Question

In Grammar and Vocabulary for First Certificate (Prodromou, 2005), Chapter 2 covers "the future", "be going to", "present continuous", and "present simple". I put three of the End-Of-Chapter questions below with the corresponding back-of-the-book answers. My concern is with Question #1 only. (I wrote #2 and #3 for context.)

Put the verb in brackets into the most suitable form of the future.

1. "What ________ you __________ this evening?" (do) 'Nothing.' [Answer: are ... doing]

2. "Well, _______ we ___________ to that new pizzeria?" (go) [Answer: shall ... go]

3. In 2004 the Olympic Games _________ in Athens. (take place) [Answer: will take place]

For Question #1, the only answer in the back-of-the-book answer is the present continuous: "What are you doing this evening?" This has effectively ruled-out the possibility of using 'be going to' to complete the sentence. In other words, I think what he is saying is that "What are you going to do this evening?" is incorrect.

Do you think he is right?

Answer 1

I agree with you: What are you going to do this evening? is just as acceptable and ordinary way of asking this question as What are you doing this evening?

Within the given parameters, so are:

What will you be doing this evening?
What are you going to be doing this evening?

Even this, which is ordinarily a very stilted way of expressing it, may be appropriate and natural in some circumstances:

What will you do this evening?

But this doesn’t necessarily mean that the book is wrong; it may be that something in the instructions excludes constructions with BE going to from consideration in this particular question.