secondary enlargement

例句：

1. 1. The company plans to expand its operations in the second-tier cities.
   该公司计划在二线城市扩张其业务。
2. 2. The researcher found that the growth of the economy was mainly driven by secondary factors.
   研究者发现，经济增长主要由次要因素推动。
3. 3. The government has proposed a plan to reduce carbon emissions through secondary measures.
   政府提出了一项计划，通过次要措施来减少碳排放。