美存在于观者眼中，但艺术家的职责就是挑战这种观念。

The best time to buy stocks is when they are out of favor.

The value or worth of a man is, as of all other things, his price; that is to say, so much as would be given for the use of his power.

I don't sing because I'm happy; I'm happy because I sing.

无人机的价值在于解决行业的痛点。