留美老师带你每天说英文 第401期:感到疲倦时,喝杯咖啡

台湾籍旅美老师今天交给我们的句子是：

There's no doubt about it, drinking a coffee or any caffeinated drink when you feel tired will make you feel more alert but let's take a second to think about what coffee is.
我们都知道，当你感到疲倦时，喝杯咖啡或任何含有咖啡因的饮料，你会清醒许多，不过让我们来想一想咖啡到底是何方神圣。