obstacle

他拒绝谈话是和平的主要障碍。

His refusal to talk is the main ___obstacle to peace.

徒步者发现了一个意外的障碍挡住了他们的路。

The hikers found an unexpected ___obstacle blocking their path.

学生的另一个障碍是图书馆提前关闭。

Another ___obstacle for students is the early closure of the library.