17. The chocolate cake looks great, but I have to watch my weight.

点睛

watch作为动词原意是“看”，而这里“留意，监督”。因此，watch my weight含义为“注意我的体重”，言外之意就是不能吃这块巧克力蛋糕，否则会变胖的。

考点归纳

watch的用法还有：
Watch the birdie! 瞧这边！／照相啦！（美国俚语）
Watch for fires! 小心火灾！
Watch yourself. 留点神。
Watch closely. I'll make turns. 盯紧点，我要转弯了。
Watch your step. 小心脚下。（相当于Mind your step.）
Watch your mouth. 说话留点神。（用于警告别人，相当于Watch your tongue/language.或Be careful of what you say.）