流动式起重机工作时，必须要使自重载荷和起吊载荷对倾覆边的力矩之和（）于零，才能不出倾翻事故。
A、大
B、小
C、等于
参考答案：A
1519年-1522年，______船队首次实现了环绕地球一周的航行，证实了地球的形状是球形．
—Didn’t he go home last Sunday?
—______. And he spent all his money playing games in a net bar.
—That’s too bad.
A．Yes, he did.
B．No, he did.
C．Yes, he didn’t.
D．No, he didn’t.
