航空移动卫星通信系统AMSS中,卫星与飞机之间的通信频率为()波段的信号。
A.X
B.C
C.L
D.C或Ku
参考答案:C
有关铁代谢的正常值,下列哪项是正确的()
A.人体每天铁排泄量大于1mg
B.妊娠的妇女每天需要铁6mg
C.正常男性的贮存铁约为1000mg
D.每天从食物中摄取铁10~15mg
E.正常人体每天制造新鲜红细胞所需的铁50mg
_______of the class_______ finished the homework already.
A.Two third, has
B.Two thirds, have
C.Two thirds, has
D.Second threes, have