慢性结石性胆囊炎首选的检查方法是（）
A.腹部X线平片
B.口服胆囊造影
C.静脉胆道造影
D.经皮肝穿胆管造影
E.B型超声检查
参考答案：E
—Whose exam paper is it?
—It ______ be Li Lei's. He always forgets to write his name on it. [ ]
A. can
B. must
C. mustn't
D. can't
当汽缸内壁温度高于外壁温度时，其汽缸内壁受（）作用。
