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Thinking SpainI said, 'It's wrong' and he said, 'Why' and I said, 'Because you are not asking about the subject, but about what the subject used to be'. Am I right?
Yes. Another way to look at it: Tom is the subject, and Tom is in the question, so Tom can't be the answer.

Consider:

Tom threw a ball. <<< A statement with only one verb - no auxiliaries.

To form a question from a sentence like the one above, you add "do-support" before inverting subject and verb:

Tom threw ...(what?)... > What Tom threw? > What Tom did throw? > What did Tom throw?

Tom used to be a bus driver. Same process.

Tom used to be (what?) > What Tom used to be? > What Tom did use to be? > What did Tom use to be?

____

Contrast:

Tom threw a ball. > Who threw a ball?

But you knew all this already. Emotion: smile

CJ
Hi Jim,

But only 'What did Tom use to be' is right!

But you knew all this already.It seems that this time I did. Emotion: nodding

Even though I did, I've never seen the process that you've explained.

Best

TS
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