定义一个函数实现交换x和y的值，并将结果正确返回。能够实现此功能的是  

A、<span style="line-height: 18.88888931274414px;">swap(int x, int y){ int t; t=x; x=y; y=t; }</span>

B、<span style="line-height: 18.88888931274414px;">swap(int *x, int *y){ int t; t=x; x=y; y=t; }</span>

C、<span style="line-height: 18.88888931274414px;">swap(int *x, int *y){ int t; t= *x; *x = *y; *y=t; }</span>

D、<span style="line-height: 18.88888931274414px;">swap(int *x, int *y){ int *t; t=x; x=y; y=t; }</span>