The sky darkens early in winter.

我在冬天常睡得较早。

But doubt darkens his expression.

但是表情却表现出怀疑。

Clouds heap upon clouds and it darkens.

云霾堆积，黑暗渐深。

Snow darkens pictures sewn on banners red.

雪暗凋旗画.

And if house prices fall, the picture darkens.

而且如果房价下跌的话, 形式会一片黑暗.

Melanin darkens the skin and is the cause of suntan.

黑色素使皮肤变黑是人被晒黑的原因.

Uncertainty darkens the future of radio and television.

不定因素使无线电和电视的前途黯淡.

Adding white lightens a color and adding black darkens it.

加入白色会使一个颜色变浅，而加入黑色则会让它变深。

As the roast darkens, caffeine and acidity decrease proportionately.

烘焙度越深, 咖啡因含量越少,酸度也越小.

Well, I must go in now, and you too. It darkens.

好吧，我得进去了，你也一样，天黑下来了。