天空的颜色很纯净。

The color of the sky is very ___pure.

这块金子是纯的，没有掺杂任何杂质。

This gold is ___pure, without any impurities mixed in.

山里的空气非常纯净，没有任何污染。

The air in the mountains is completely ___pure, with no pollution.

这完全是浪费时间。

This is a ___pure waste of time.