按照换热方式来分，换热器可分成哪几种？
参考答案：
间壁式换热器、蓄热式换热器、混合式换热器三种。
Shopping online can save much time as you _____ go to a shop or walk around crowded shopping centers.[ ]
A. don't have to
B. oughtn't to
C. won't
D. mustn't
诊断明确后，进一步的处理是
A．继续观察
B．手术治疗
C．输血
D．静脉滴注抗生素
E．口服止血血药物
