20以内的质数有几个?[ ]
A.7
B.8
C.9
答案:B
Model as a career _____ to many young girls because of the fascinating T-stage. [ ]
A. attracts
B. appeals
C. calls
D. pulls
在数控系统中,相对坐标和绝对坐标混合编程时,同一程序段中可以同时出现()。
A、X与U
B、Z与W
C、Y与V
D、U与Z