[单项选择]有如下程序：
#include＜iostream．h＞
long fib(int n)
if(n＞2)return(fib(n-1)+fib(n-2))；
else return(2)；
void main（　）
cout＜＜fib(3)；
该程序的输出结果是
A. 2
B. 4
C. 6
D. 8

The role of the farmer has always been an important one. Two hundred
years ago, 95% of American workers were farmers. Agriculture is 62. ______.
America’s biggest industry. Today, less than 3% of American workers are
farmers. Yet agriculture still is America’s biggest industry, it employs more
workers than any other industry, and it produces more food than Americans
can consume enough to make the United States the world’s largest importer 63. ______.
of agricultural goods. American farmers used to grow only enough food to
feed their families and animals. Now each farmer grows enough to feed 78
other people. American farmers produce more today because they have to
use modern farm and business methods. This means they have to know more 64. ______.
than ever before. They still learn about soil, the weather, ha