New words：

cocoon[kə'ku:n]

n.茧；软罩；保护膜；防护层
v.把…包围起来保护；（用…）完全保护起来

Sample Sentences：

Most worms cocoon in winter.
A cocoon is a kind of silk covering made by an insect.
The children tore the cocoon open to see if there was a pupa.
We were warm and safe, cocooned in our sleeping bags.

silk [silk] n.丝绸；（蚕）丝；丝织物

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