重点讲解：
1. back up 支持，证实（某种说法）；
Radio signals received from the galaxy's centre back up the black hole theory.
从该星系中心收到的无线电信号证实了黑洞理论X#)eT8TlzuIo[。
2. tell apart 区分；区别；辨别；
It's difficult to tell them apart.
很难把他们区分开来43GjMsK.T[p)26]nxO8。
3. on top of 另外；加之；除…之外(还)；
On top of that, I've got one extra bit of good news I think you might want to hear.
除此之外，我还有一个你想要听到的好消息#!vD3^*L0YBd!。
4. encourage sb. to do sth. 鼓励；激励；
Relocation expenses were paid to encourage senior staff to move to the region.
公司发放了安置费来鼓励高级员工搬到这个地区xur;t2(T])Z@ddwlBg3&。