From the teacher’s patience and understanding, I have learnt what a big responsibility______is to educate us.

A．this

B．that

C．it

D．one

爆破地震波与天然地震波最大的区别是（）。

A.爆破地震波频率比天然地震波高

B.爆破地震波频率比与天然地震波低

C.一样

D.无法确定