—I think it’s very dangerous to drive six hours without a rest.
—I agree. Six hours really a very long time.
A. has
B. is
C. were
D. am
网友回答
A. has
(答案→)B. is
C. were
D. am
解析：根据题干可知本句的意思应该是“六小时真的是很长的一段时间。”而has表示“有”，所以应该排除；通过意思，我们知道，此句是一般现在时，所以C是错误的；am用于I之后，所以D也是不对的。另外，当时间作主语是谓语动词要用单数。所以本题选B。