en作为后缀的单词

　　He needs to sharpen up before the Olympic trials.

　　在奥运会选拔赛之前，他需要进一步提高自己。

　　The outline of the trees sharpened as it grew lighter.

　　随着天色转亮，树的轮廓变得清晰了。

　　The sky began to darken as the storm approached.

　　暴风雨来临时天空变得黑沉沉的。

　　Luke's face darkened.

　　卢克沉下脸来。

　　The building was darkened except for a single light burning in a third-story window.

　　整座大楼一片漆黑，只有3层的一个窗户透出一丝光亮。

　　When the days shorten in winter some people suffer depression.

　　冬季天短，有些人会变得抑郁消沉。

　　As they shorten, cells become more prone to disease and death.

　　细胞变小后就会更容易感染疾病，也更容易死亡。