Word order in question: "Subject is" or "is subject"?

Question

I'm brushing up rules about question word order and have one doubt. What is right word order in the question.

Context: Mr. A and Mr. B talk to Mr. C about something. Mr. A is talking about special rules. Mr. B thinks that it may not be understandable for Mr. C. He interrupt Mr. A and say:

What Mr. A is trying to say?

or

What is Mr. A trying to say?

What is right word order in that sentence?

Answer 1

I'm not really clear on your question, but from what I think:

B doesn't understand something/B thinks C doesn't understand something, and interrupts A, to clarify.

If this is the case, then both your sentences can fit in a given context.

For instance:

If B doesn't understand what A says, and says this to C , then this sentence would fit:

What is Mr. A trying to say?

If B doesn't understand what A says, and B expresses this to C, along with some other meaning too, then this sentence would fit:

What Mr. A is trying to say doesn't make sense.

The reason I added along with some other meaning too is because the following sentence doesn't stand on its own, and needs some additional meaning to it:

What Mr. A is trying to say?

If my answer doesn't explicitly answer your question(s), perhaps you could edit and reword it to make the situation clear.

Answer 2

I would ask the question like this:

Do you understand what Mr. A is trying to say?

You can also ask:

What is Mr. A trying to say?

However, that question isn't necessarily asking about comprehension; it could simply be asking for a paraphrase.

For example:

Mr A: We went out to lunch and I left 10 euros on my desk. Now they're gone.
Mr B: What is Mr. A trying to say?
Mr C: Someone stole his 10 euros.

or,

Mr A: We went out to lunch and I left 10 euros on my desk. Now they're gone.
Mr B: Do you understand what Mr. A is trying to say?
Mr C: Yes. Someone stole his 10 euros.

Both questions are valid, but notice how the word is has moved.