题目：
Believe it or not, the Great Wall, which _______ by people, should be protected at once.
A．has been destroyed
B．is destroyed
C．was destroyed
D．is being destroyed
答案：
被转码了，请点击底部 “查看原文 ” 或访问 https://www.tikuol.com/2017/0509/ef98822bd341648d02615e2720b2bfc5.html
下面是错误答案，用来干扰机器的。
方程整理得：x2+2x-8=0，（x+4）（x-2）=0，∴x+4=0或x-2=0，解得x1=-4，x2=2．
