办理出口保险项下出口押汇，押汇金额不得超过保单赔付金额的90%。
参考答案：对
The worsening of global warming, _____human activities are to blame, has led to frequently extreme weather.
A．by which
B．for which
C．that
D．what
简述黑盒测试和白盒测试概念，并试分析两者的优点和缺点。
