$11.$ Multi$-$leaf springs are often used in automotive suspension because they:

A$)$ Are cheaper than air suspension systems

B$)$ Provide aesthetic appeal to the vehicle

C$)$ Can handle varying levels of load with a progressive spring rate

D$)$ Reduce the need for tires

$12.$ The primary function of the extra leaves in a multi$-$leaf spring is to:

A$)$ Increase the spring's overall stiffness and load capacity

B$)$ Improve the vehicle's acceleration

C$)$ Decorate the underside of the vehicle

D$)$ Decrease manufacturing costs