他把刀插回刀鞘里。

He slid the knife back into its ___sheath.

竹笋在生长时会从坚硬的鞘中钻出来。

The bamboo shoot grows out of its tough ___sheath.

她穿着一条修身的米色连衣裙参加晚宴。

She chose a beige ___sheath for the evening party.