大多数可编程序控制器采用()进行程序输入和更改的操作
A、编程器
B、键盘
C、显示器
D、操作器
参考答案:A
The first textbooks _______ for teaching English as a foreign language came out in the 16th century.
A.having written
B.to be written
C.being written
D.written
生物体主要靠有机分子的氧化获得能量。