（）传动的瞬时传动比恒定。
A.齿轮
B.带
C.链
D.摩擦轮
参考答案：A
—__________do you read English books?
—Twice a day. [ ]
A. How many
B. How much
C. How long
D. How often
可引起胆囊肿大伴有压痛的疾病是（）
A.急性胆囊炎
B.慢性胆囊炎
C.胆囊癌
D.胰头癌
E.肝癌
