Answer:
When
Explanation:
Clause is a group of words that usually consists of subject and predicate. There are two types of it: independent ( it can stand alone as a sentence) and dependent ( it can not stand alone). Types of dependent clause: adverb, adjective, noun dependent clause. Adverb clause modifies the meaning of a verb, adjective, another clause etc. It usually starts with although, if, after...
In the given sentence adverb clause is After I went to bed last night and it answers the question when did the telephone ring.
