a barrier to progress的用法和样例：
- Poor health may be a barrier to success.
- Heavy duties on imports and exports are a barrier to international trade.
- In vitro mature (IVM) rate and pathenogetic activation rate ofporcine oocytes, at present, are still low, which become a barrier to progress in research ofporcine embryonic engineering.
- Poor health may is a barrier to success.
- "The system is working as a barrier to recruitment.