John had to start work at an early age, ____ his family was very poor.

A．or

B．so

C．but

D．because

属于清燥救肺汤组成药物的是（）

A．石膏、知母

B．石膏、人参

C．石膏、粳米

D．石膏、牛膝

E．石膏、寒水石