Desertification，the name for ______ happens when farmable land is turned into desert，is a growing world problem.

A．which

B．where

C．what

D．How

以下程序的输出的结果是( )。
#include ＜iostream.h＞
void main()

int i,k,a[10],p[3];
k=5;
for(i=0;i＜10;i++) a[i]=i;
for(i=0;i＜3;i++) p[i]=a[i*(i+1)];
for(i=0;i＜3;i++) k+=p[i]*2;
cout＜＜k;

A. 20
B．21
C. 22
D．23