重点讲解：
1. on hold 推迟；中断；
The project is on hold until more money is available.
这项工程暂停，等到有更多的钱时再进行*sP2W!Cz&33。
2. knock over 撞倒；
He was knocked over by a bus and broke his leg.
他被一辆公共汽车撞倒，一条腿折了IVb|(xG3a|TFI。
3. be based on 以…为基础；
The selection process is based on rigorous tests of competence and experience.
选拔过程是基于对能力和经验的严格测试sn%J].aCHU,;yA!oVPZ。
4. be unlikely to do sth. 不太可能的；未必会发生的；
As with many technological revolutions, you are unlikely to be aware of it.
就像诸多的技术革命一样，你可能不太会注意到它z=FpJ)c|(#@。