困难的名词复数

　　Cases of breathing difficulties increase in lockstep with air pollution.

　　呼吸困难的病例随空气污染的加剧而增加。

　　The difficulties in her way merely strengthened her resolve.

　　她所遇到的困难只是让她更加坚定。

　　Several pupils were designated as having moderate or severe learning difficulties.

　　几名学生被认定有一定或严重学习困难。