编写求两个双精度之和的函数,选项中正确的是()(2分)double add(double a,double b)
{double s;
s=a+b;
return s; }
double add(double a,b)
{double s;
s=a+b;
return(s); }
double add(double a double b)
{double s;
s=a+b;
return s; }
double add (a,b)
{double a,b,s;
s=a+b;
return(s); }