数控编程在同一程序段中同时指定两个或两个以上M代码，则（）。
A、第一个有效
B、最后一个有效
C、均无效
D、同时有效
参考答案：B
Where is the book?[ ]
A. There it is.
B. It's a book.
C. My name is Jenny.
– I don’t know ______ now.
– She’s much better today.
A. where she is B. how she is C. how is she
