Fuel enters the cylinder in the ______.
A.first stroke
B.second stroke
C.third stroke
D.the final stroke
The scenes have to be filmed many times because ______.
A.it takes a long time to make a film
B.it is often difficult to make them just right
C.many people work together
D.the film is poor
工业上通称的PC机是指()。
A.顺序控制器
B.工业控制器
C.可编程控制器
D.PC微型计算机
计算机病毒是一段程序,一般隐藏在______中。
A.控制器
B.运算器
C.只读存储器
D.可执行文件