[rewboss]

Ooh, it's complicated...

You see, "be" is a special verb.

All verbs have a subject: many common verbs also have one or more objects. Objects and subjects do not (normally) refer to to the same thing:

Peter would read the newspaper (if he had time).

"Peter" and "the newspaper" are clearly different things; "Peter" is the subject, and "the newspaper" is the object.

When we form a question, we can replace the subject with a question word (or "interrogative pronoun"). In that case, we don't actually change the word order:

Who would read the newspaper?

But if we replace the object with a question word, we must change the word order and swap the subject and the auxiliary verb, as well as putting the question word first in the sentence:

What would Peter read?

But now consider this:

Peter is an American.

"Peter" is the subject, but what is "an American"? You might think it's the object, but if you think about it, "Peter" and "an American" both refer to the same person. So it's a kind of half-object, a not-quite object that's also the subject. This strange half-subject half-object state is one of many reasons people sometimes argue about whether we should say "It is I" or "It is me".

So we put "be" in a special category all of its own: we call it a "cupola", and instead of an object, we say it has a "complement".

And as a cupola, "be" follows its own rules.

Take this sentence:

Your last meal would be chicken and rice.

"Your last meal" is the subject, and "chicken and rice" is the complement. But we could write it differently, with little change in meaning, because the subject and complement refer to the same thing:

Chicken and rice would be your last meal.

That might change the emphasis of the sentence, but it doesn't change the meaning. We have two sentences that mean the same thing.

Now, for each sentence, let us replace "chicken and rice" with "what".

In the first case, "chicken and rice" is the complement. We follow the same rule we follow when replacing an object with a question word: the question word goes first, and then comes the auxiliary verb, followed by the subject and the main verb:

What would your last meal be?

In the second case, "chicken and rice" is the subject. Now we simply replace the subject with the question word, and we don't need to change the word order:

What would be your last meal?

Let's study these sentences again:

Peter would read the newspaper -> What would Peter read?
Your last meal would be chicken and rice -> What would your last meal be?

Peter would read the newspaper -> Who would read the newspaper?
Chicken and rice would be your last meal -> What would be your last meal?

As I said, it's complicated. But in effect it means this: With "be", in a question with a question word and an auxiliary verb, you often have a choice where to put "be".