一英语选择What time is it （）your watch?It's eight fifteen.

一英语选择What time is it （）your watch?It's eight fifteen.
What time is it （ ）your watch?It's eight fifteen.A、on B、at C、in D、by 着类题我很郁闷都读的通不知道怎么选请各位大侠帮忙 怎么选用什么方法判断