一道语法题

xiaobushi

PPview test2-4中的 101. The (migration route) of the first humans to occupy  North America took (them across) a land bridge that  once (was connected) Asia with (what) is now Alaska.

答案为什么会是C？
that既然指的是a land bridge ，后面用was没有错啊？

请高手帮我解答一下，谢谢！

xiaobushi

谢谢fdkbaby！
但好像有be conncected with 这个词组吧，比如：
That solitary old man was suspected to be connected with the crime.
那个孤独的老头被怀疑与犯罪事件有关。

xiaobushi

牛人就是不一样！