Multiple choice Where does silk come from? Man-made from plastic From seeds of cotton plants From cocoons of caterpillars From the stem fibers of flax plants Reveal answer Fill a bubble to check yourself C Correct answer Explanation Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae, such as silkworms, to form cocoons.