问答题,简答题：基准物质的条件之一是摩尔质量要大，为什么？

[交际用语]I'd like to open a current account._________

[交际用语]Would you mind lending me your car tonight _________ I have to study ...

203[交际用语]I can't catch up with the rest of the class. The subjects are diffi...

[交际用语]I wonder what the weather will be like tomorrow._________

FD指引杆有几个（）A．俯仰杆、横滚杆；B．偏航杆；C．A和B。