$7.$ In helical spring design, what role does Wahl factor play?

A$)$ It determines the color of the spring

B$)$ It accounts for the curvature effect on spring stiffness

C$)$ It measures the electrical conductivity of the spring material

D$)$ It's used to calculate the spring's resonance frequency

$8.$ What is a critical consideration in the optimum design of helical springs for dynamic loads?

A$)$ Aesthetics of the spring design

B$)$ Ensuring a minimum safe distance between coils

C$)$ Color coordination with the machine

D$)$ Maximizing the spring's extension length