What does covered mean?

[Stupy]

English Grammar Tests, Elementary Level

ESL/EFL Test #166 "The Platypus: Vocabulary Practice", question 4

Like a cat, a platypus is covered in ......... that helps keep it warm.

(a) scales
(b) bristles
(c) spikes
(d) fur

English Grammar Tests, Elementary Level

ESL/EFL Test #166 "The Platypus: Vocabulary Practice", answer 4

Like a cat, a platypus is covered in fur that helps keep it warm.

Correct answer: (d) fur
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covered

[Mister Micawber]

overlaid or spread or topped with or enclosed within something
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Native English teacher at Mister Micawber's