You can read        list and select an item from it just like you choose                                  _____ dish by reading the menu.

A．the; the

B．a; a

C．the; a

D．a; the

蒸汽压缩式理论制冷循环的热力完善度是( )。

A．实际制冷循环的制冷系数和相应高低温热源的逆卡诺循环的制冷系数之比
B．实际制冷循环的制冷系数和理论循环的制冷系数的比值
C．理论循环的制冷系数和相应高低温热源的逆卡诺循环的制冷系数之比
D．理论循环的制冷系数和轴功率之比