The visible part of the ear has the ability to stretch significantly, and then recoil back to its original position. Which protein fiber must be present?

Elastic Fibre

Explanation:

Due to its ability to stretch and return to it's Normal size. It is one of the three main types

hydrogen is a compound or a single element and a element is a pure substence that cannot be separated into simpler subtances

clorine is a compound its a chemical substance that forms when two or more different elements combine

so both hydrogen and clorine are compounds