They're all famous _____.[ ]
A. swim
B. swimmer
C. swimers
D. swimmers
答案:D
Listen! Someone ________ an English song now.[ ]
A. sings
B. sang
C. is singing
D. was singing
风力发电机组中,测量温度用PT100在室温下阻值正常为()
A.90—100欧姆
B.100—120欧姆
C.120—140欧姆
D.正的无穷大