螃蟹会定期蜕壳以适应身体生长。

Crabs regularly ___slough their shells to accommodate growth.

蛇每年都会蜕去旧皮。

Snakes ___slough their old skin every year.

连续失败后，他陷入了深深的绝望之中。

After repeated failures, he sank into a ___slough of despair.

我们小心翼翼地穿过那片泥泞的沼泽地。

We carefully walked through the muddy ___slough.