1.a harbinger for sth. 预示着
What of China's past could be a harbinger for its future?
中国过去的哪些经历能够预示其未来？

2.over an extended period of time 在相当长的一段时间内
The securities business has developed over an extended period of time, and embodied different features in different countries and periods.
证券市场已经发展了相当长一段时间，而且，不同的国家、不同的时期，其展现出不同的特点也不一样]fk,gAZgR_Hooc。

3.boots on the ground （派遣到当地去完成某一任务的）人力
"You simply have to have the boots on the ground to manage the fisheries," he said.
他说:“没办法，你只能部署人员到当地管理那边的渔业Dzz@O%)5*nqJBP^。”

4. at the mercy of 在……的掌控之下
Farmers are often at the mercy of the weather.
农民常常要受天气的摆布G1aFhLkxic-GB8.-HyW。