警报声根据所发出的声音的长短、间隔时间的不同分为（）种。
A、1
B、2
C、3
D、4
参考答案：C
法人以它的注册登记地为住所。 ( )
When she returned back by abroad, she told us all about her experience as an illegal immigrant.()
A. by
B. back
C. from
D. back from
