1.look back 回顾；倒退

And I look back with pride and amazement.
而当我回顾过去时，心中充满自豪和惊叹。

Understanding the tata connection requires a look back at history.
要了解塔塔之间的种种联系需要回顾一下它的历史。
2.propel to 推至

Conversely, employees who represent the brand flawlessly and consistently can propel a business to stardom.
反过来,雇员代表和维持品牌可以推动企业不断轻声呼唤。

Experts say several factors have helped propel moocs to the center of the education stage, including improved technology and the exploding costs of traditional universities.
专家表示有几个原因把moocs网教推向了教育舞台的中央，包括科技的日新月异，还有传统大学天价的花费。

3.set off 开始；引起

Nichols set off for his remote farmhouse in Connecticut.
尼科尔斯动身去他在康涅狄格州的偏僻农舍了。

The President's envoy set off on another diplomatic trip.
总统的使节开始了又一次外交之旅。

4.focus on 致力于；使聚焦于

That's all you want to focus on.
你只需将你的注意力集中于此。

The project also will focus on key secreted pathogenic proteins.
该项目也将集中于主要分泌性致病蛋白质。