When travelling in buses or trains,we are likely to have conversations _____ we give information or opinions about different things.     

A．where

B．which

C．what

D．when

在我国，测定血清胆固醇的参考方法是

A．ID-MS法
B．ALBK法
C．HPLC法
D．胆固醇氧化酶法
E．以上皆不是