航班延误给我们的旅行计划带来了额外的麻烦。

The flight delay caused an unexpected ___complication to our travel plans.

手术后他出现了感染并发症。

He developed an infection ___complication after the surgery.

这个数学问题有很多复杂的细节，导致学生们难以理解。

The math problem has many ___complications that make it hard for students to understand.