硅胶管的特点是()
A.质地柔软、无毒
B.耐高热和低温
C.有短期抗凝作用
D.能用任何消毒剂擦拭或浸泡
E.长期置于血管内不会引起异物反应
参考答案:A, B, C, E
杂物电梯轿厢地坎和层门地坎之间的水平距离不大于()mm.
A.25
B.50
C.100
—Could you please come to the museum with me this afternoon?
—Sorry,I ________.I have to take a piano lesson at 2 pm.
A.couldn’t
B.mustn’t
C.can’t
D.needn’t