The train （ ）to arrive at 11:30, but it was an hour late.

The train （ ）to arrive at 11:30, but it was an hour late.

was supposed 

is supposed

supposes

supposed

本题考查固定搭配。

be supposed to do sth.：应该做某事。根据后面的was可知，前半句也应用一般过去时。

句意：火车本应11:30到达，但晚了一个小时。

所以本题选A。