生产经营单位必须为从业人员提供符合国家标准或者()标准的劳动防护用品。
A.行业
B.该单位
C.当地
D.国际
参考答案:A
Speaker A: Could I trouble you to return these two books for me Speaker B:_____
A.It's no trouble at all.
B.Yes, please.'
C.Why didn't you go to the library yourself
D.Sure, I'll be glad to.
若串s="MathTypes",则其子串的数目是【 】。