血管分为动脉、静脉、（）。
A.排泄管
B.导管
C.毛细血管
D.分泌管
参考答案：C
标准煤是低位发热量为（）的煤。
A.7000大卡/公斤
B.8000大卡/公斤
C.9000大卡/公斤
--- Why don’t you ask him for help? You _____ be good friends.
--- We have disagreements and we haven’t talked to each other for a long time.
A．are used to
B．are used for
C．are used as
D．used to
