He's gone to the library ,_______ he ?
A:isn't
B:doesn't
C:hasn't
D:wasn't
将下列句子改为陈述句。
①它一听到弦响,心里怎么能不害怕呢?
②对浪费能源的现象,我们怎么能容忍呢?
100厘米=( )