It was from only a few supplies that she had bought in the village _____the hostess cooked such a nice dinner.

A．where

B．that

C．when

D．which

方程x²+ax+b=0的两实根之差的绝对值为．

(1)方程x²+ax+b=0的两实根之比是3:4；(2)方程x²+ax+b=0的判别式△=2．