VHF/70 CHEPIRB S-EPIRB发射遇险报警时,其电波采用()传播
A.天波
B.地波
C.空间波
D.波导
参考答案:C
All the apartments have been sold out while the building is still _____.
A.Constructed
B.constructing
C.under construction
D.in construction
在无特定要求和规定情况下,转盘扭矩呈趋势性增大()%以上,或大幅度波动称为异常。
A、10
B、20
C、30
D、50