这把刀非常锋利，小心使用。

Zhè bǎ dāo fēicháng fēnglì, xiǎoxīn shǐyòng.

This knife is very sharp, use it carefully.

剪刀的刀刃应该保持锋利。

Jiǎndāo de dāo rèn yīnggāi bǎochí fēnglì.

The blades of scissors should be kept sharp.

这把剪刀新磨过，非常锋利。

Zhè bǎ jiǎndāo xīn mó guò, fēicháng fēnglì.

These scissors have been freshly sharpened and are very sharp.