He the book for a whole week.[ ]
A. has borrowed
B. borrowed
C. has kept
D. kept
答案:C
新危险物标可以装设雷达应答器,并发出莫尔斯信号“D”,在雷达屏幕上莫尔斯信号的长度为()。
A.0.5nmile
B.1nmile
C.1.5nmile
D.2nmile
保证测量仪器规定的准确度、满足误差在规定极限之内的量值范围,即为()。
A.标称范围
B.测量范围
C.示值范围
D.量程