beggars can’t be choosers字面意思“乞丐不能挑三拣四”，引申为不能挑三拣四，不能挑肥拣瘦。

【例句】
In this village you are only going to get these many options for furniture. Learn to live it because beggars can't be choosers.
在这个村子里，可买的家具就只有那么多。学会活下去，不能挑肥拣瘦。

You asked for this and now you want me to exchange it? Don’t you know that beggars can't be choosers?
你要这个，现在你要我换？难道你不知道不能挑三拣四吗？