回顾性调查时
A．按小时进行统计B．按日进行统计C．按月进行统计D．按年进行统计E．不必按时间进行统计
参考答案：E
I like koalas. They sleep ______the day, but at night they get up.[ ]
A. during
B. before
C. on
D. after
SG400/140－50410型锅炉的再热蒸汽流程是怎样的？
