.

______the zoologists tried to prove was that the photo of the South China Tiger had been staged or technologically dealt with.

A．That

B．Why

C．Whether

D．What

有下列程序：
int fun(int n)
if(n==1)return 1；
else
return(n+fun(n-1))；

main()
int x；
scanf("%d"，&x)；x=fun(x)；printf("%d\n"，x)；

执行程序时，给变量x输入10，程序的输出结果是( )。

A．55

B．54

C．65

D．45