长期的压力可能导致大脑功能的退化。

Chronic stress may cause ___degeneration of brain function.

随着年龄增长，关节退化会导致行动不便。

Joint ___degeneration can cause mobility problems as people age.

许多历史学家认为这是文明退化的标志。

Many historians see this as a sign of cultural ___degeneration.