Nobody knew what they had been doing all these years.

　　沒(méi)有人知道他們這些年都在干什么。

　　Until this summer, China had been doing that carefully.

　　截止今年夏天，中國一直在審慎地這么做。

　　At that point, he realized what he had been doing all along.

　　在那時(shí)，他才意識到他一直在做的事。