specific pathogen free flock

例句：

1. 1. The hospital'spolicy of specific pathogen free flock is amajor concern for many parents.
   医院的无特定病原体群政策是许多家长的担忧。
2. 2. Theresearchers are working on developing a specific pathogenfree flock to prevent the spread of disease.
   研究人员正在努力开发一种无特定病原体群，以防止疾病的传播。
3. 3. The governmenthas announced plans to implementa specific pathogen free flock inorder to protect public health.
   政府宣布了一项计划，旨在实施无特定病原体群，以保护公共卫生。