Adverb clauses are group of words used in shifting or adding meaning of a verb, clause, adjective, or another adverb. These clauses can be used if: firstly, a sentence contains a subject and a predicate. Secondly, when a subordinate conjunction is used and thirdly, if it answer the ‘adverbial questions’ – when, why, when and how. It is also further categorized to time, place, manner, degree, condition, concession and reason.
In the sentence: After I went to bed last night, the telephone rang twice.
The adverb clause of time is ‘after I went to bed last night’, so the question must be in ‘when’ form. That is: When did the telephone ring twice?