A. When
B. Why
C. in
D. What
Mike: ____ is your favourite season ,Sarah?
Sarah: Summer.
Mike: ____ do you like summer?
Sarah: Because we wll have a party at home 0n Children's Day.
Mike: ____is Children's Day?
Sarah: It's ____ Jane.
用一束紫外线照射某金属时没有产生光电效应,下列措施中可能产生光电效应的是( )