Which of the following statements concerning adverbial clause of time is NOT true？

A.“As” can also be used when we want to say that when one thing changes， another thing changes at the same time.

B.“when” is often used to talk about an event that takes place at the same time as some longer action or event described in the main clause.

C.“While” is used when you are mentioning a time or event in the past and indicating that a situation has continued from then until now.

D.In formal speech and writing， we can often leave out “subject + be” in clauses with “when” and “while” if the main and subordinate clause refer to the same subject.

正確答案：“While” is used when you are mentioning a time or event in the past and indicating that a situation has continued from then until now.