word choice - What causes X or What does cause X?

What causes coral bleaching ?

What does cause coral bleaching ?

What is the difference ?? which is grammatically correct ?

Thank you in advance.

Answer

USE THIS: What causes coral bleaching?
NOT THIS: What does cause coral bleaching?

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This is one of the most common errors made by learners. Presumably, it usually happens after learning auxiliary verbs (be, do, have) and the subject-verb-inversion in Yes/No questions.

How can we deal with it?

Here is a good rule of thumb: keep in mind that What and Who questions can ask for the subject or the object of the verb. And it depends on what we ask about.

• If the What (or Who) question asks for the object of the verb, we invert the subject and the auxiliary verb like we do in Yes/No questions. For example,

"What is this?" "This is a book." -- (a book is the object of the verb is)
"What did you say?" "I said, 'Hello'." -- ('Hello' is the object of the verb said)
"Who will you hire?" "I'll hire John." -- (John is the object of the verb will hire)

• If the What (or Who) question asks for the subject of the verb (and thus the subject of the sentence, when the sentence is a simple sentence), we DO NOT invert the subject and the auxiliary verb. In other words, we use the normal word order: the same word order as we use in declarative sentences. For example,

"What fell on him?" "A book fell on him." -- (A book is the subject of the the verb fell)
"Who owns this house?" "Jake owns this house." -- (Jake is the subject of the verb owns)

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In your sentence, you need What causes coral bleaching?, because you ask for the subject of the verb causes (so an answer could be something like: The rise of sea temperatures causes coral bleaching, where The rise of sea temperatures is the subject of the verb causes).

We don't normally use the other alternative, "What does cause coral bleaching?". (It could be used the same way we could use I do like it.) Avoid using it.