The scientists all over the world are trying their best to develop _____ energy, such as sunlight, wind and

water for power and fuel. [ ]

A. unique

B. alternative

C. primary

D. instant

以下程序运行后的输出结果是 【6】 。
#include ＜stdio.h＞
int a=5;
fun (int b)
static int a=10;
a+ =b++;
printf("%d",a);

main()
int c=20;
fun(c);
a+ =c++;
printf("%d\n",a);