粪便肉眼观呈果酱样脓血便，病因多为（）
A.阿米巴痢疾
B.出血性小肠炎
C.痔疮
D.急性菌痢
E.直肠息肉
参考答案：A
锅炉的分类中，按( )可分为燃煤锅炉、燃油锅炉、燃气锅炉等。
A．载热介质 B．锅炉结构C．热能来源 D．燃烧方式
A hydrostatic release mechanism for a liferaft（）.
A.must be wet before it will release
B.should be kept in a watertight cover except in an emergency
C.will inflate the raft in its cradle if operated manually
D.must be submerged to a certain depth to release automatically
