现已发现、人造的118种元素中，有（）是构成生物体的。
A.二十几种
B.三十几种
C.四十几种
D.五十几种
参考答案：B
无线局域网的国际标准是（）.
A.IEEE802.3
B.IEEE802.4
C.IEEE802.5
D.IEEE802.11
I hear a number of workers in the factory _____ out of work and the number of them ______ quite large .
A． are , is
B．is , are
C．is , is
D．are, are
