题目

If the students who killed themselves had only been more confident, their deaths ________． A．need have been avoided                               B．must have been avoided C．might have been avoided                              D．will have been avoided 答案：C正常人的心脏推动血液流动的功率约1.5W，那么在一天时间内心脏做功    J，这些功可以把一个质量为60千克的人匀速举高    m．