1. WHO believes that, as AIDS becomes more common, the disease promises to unite the world to a degree never seen before.
    世界卫生组织认为随着艾滋病越来越常见，它有可能使整个世界以前所未有的程度联合起来。

2. Unite and form a league against imperialism.
    团结起来组成一个反帝同盟。

3. I learned how my mother, through means only available in this country, would finally be able to unite my great-grandmother with my grandfather again.
    我知道了妈妈是怎样通过只有在这个国家才能找到的渠道，最终成功地使我外曾祖母和外公重新团圆的。