It should be C. because interrogative pronouns are used to ask questions.
The sentence that is correctly construed with an independent clause and a dependent clause is A) As they examined the evidence afresh, they thought of a completely different explanation.
The other sentences don't have dependent clauses, only phrases.
Answer:
the correct one is the Read the sample sentences in the dictionary or thesaurus to see how each word is used
Answer: look in the comments for the answer if it's still there please I wrote it myself and thought it was pretty good to make up one on the spot u might have to scroll up a bit to find it but it's there