题目选项分析

At approximately 22 weeks, a fetus becomes fully covered by lanugo, or a fine, soft hair that insulates the body until fat deposits accumulate in the wrinkles of the skin, often remaining until birth.

At approximately 22 weeks, a fetus becomes fully covered by lanugo, or a fine, soft hair, which insulates the body until fat deposits accumulate in the wrinkles of the skin, and which often remain until birth.