单项选择题

关于自定义函数的语法结构书写正确的是()

A.int function sum(int num1,int num2){return num1+num2;}
B.function sum(var num1,var num2){return num1+num2;}
C.var function sum(num1,num2){return num1+num2;}
D.function sum(num1,num2){return num1+num2;}