— Is that girl in red Sally?

—No, it _________ her. She has gone to Hong Kong.

A. may be          B. must be         C. can't be

用于热生物传感器的换能器，必须能将某种能量转换为其他可识别的信号，这种能量是（）

A.机械能

B.电能

C.热能

D.声能

E.化学能