propagation time

例句：

1. 1. The bacteria are responsible for the propagation of disease.
   细菌负责疾病的传播。
2. 2. The propagation time for this virus is relatively short.
   这种病毒的传播时间相对较短。
3. 3. The propagation of knowledge is essential for progress.
   知识的传播对于进步至关重要。