25×55.
原式=(2×5)5
=105
=100000.
当我们用力快速地挥手时,可是还是听不到挥手的声音,是因为:( )
A.响度太小
B.音调太低
C.振动幅度不大
D.根本不振动
We should consider the students' request _____ the school library provide more books on popular science. [ ]
A. that
B. when
C. which
D. where