小肠肿瘤引起急性肠梗阻的常见机制是()
A.肿瘤堵塞肠腔
B.肿瘤缩窄肠腔
C.肿瘤压迫邻近肠管
D.肿瘤细胞产生的5-羟色胺造成肠管痉挛
E.肠套叠
参考答案:E
It's very cold outside. You'd better _____ your coat when you go out. [ ]
A. dress
B. put on
C. wear
D. have on
控制流程的每一循环始于( )。
A.转换 B.投入C.对比 D.反馈