be sure to come to our party this evening 这是祈使句,动词要用原型可以选who are, 然后理解为定语从句么1. 选who are 的话就不能构成完整句.John and Mary，who are sure to come to our party this evening后面没有谓语动词，意思不完整。2.John and Mary，who are sure to come to our party this evening，haven't come yet.看清楚没有，这才完整