如果原始凭证的金额填写错误，应( )。
A．要求对方更改
B．自己用褪色的药水更正
C．退回并要求对方重开
D．直接涂改
参考答案：C
It's extremely dangerous for the drivers to __________ speed as the traffic lights are changing. [ ]
A. pull up
B. put up
C. rise up
D. pick up
设函数f(x)与g(x)都可导，且F(x)=g(x)|f(x)|，求证： (Ⅰ) 当f(x0)≠0时，F(x)在点x=x0处必可导； (Ⅱ) 当f(x0)=0时，F(x)在点x=x0处可导的充分必要条件是f’(x0)g(x0)=0．
