Test analysis: This question focuses on the tense and word order of the object clause. No matter which sentence structure acts as an object clause, the word order of declarative sentences should be used, and the tense of clauses should be consistent with that of main clauses. The predicate verb of the main clause is the predicate verb of the past tense clause, and the corresponding past tense should also be used. If the clause expresses facts or objective facts, the simple present tense should be used regardless of the predicate verb of the main clause. According to the prompt, you can choose a.

Comments: There are three test sites for object clauses, one is the guide word, the other is the tense, and the third is the word order. Therefore, if you want to master the object clause well, you must master the relevant knowledge points in these three aspects.