we --- be careful when we'er walkung across the road there're too many cars nowa\ canb\ mayc\ mustd\ could说理由!
问题描述：
we --- be careful when we'er walkung across the road there're too many cars now
a\ can
b\ may
c\ must
d\ could
说理由!
答
c.第三个答案，此句不需要虚拟语气
答
选择C：must（必须）
我们过马路必须要小心,因为现在车子很多.