铁农具在现在生产上得到了广泛应用。我国最早开始出现铁农具是在[ ]
A．商朝时期
B．西周时期
C．春秋时期
D．秦朝时期
答案：C
Her family _____ friendly to us. We love them.
[ ]
A. is
B. are
C. be
D. am
For ships equipped with an SES, it is（）and（）for the operator to send a distress alert.
A.easy/reliable
B.difficult/cheap
C.stable/compulsory
D.easy/expensive
