$2.$ The graph below shows the stress $\backslash ((\backslash$sigma$)\backslash )$ versus percent strain $($percent strain $\backslash (=100\backslash$varepsilon $\backslash ))$ for three different fibers, whose chemical structures are shown on the following page.

a$)$ What is the approximate elastic modulus for each fiber?

b$)$ The chemical structures of the three fibers are shown on page $2.$ Match each fiber to its stress$-$strain curve and briefly explain your reasoning. $($Hint: consider the stiffness of the chains.$)$

Polymer A:

Polymer C:

Polymer B: