$7.$ In V$-$engine balancing, what is the significance of the angle between the banks?

$-$ A$)$ It affects the primary balance.

$-$ B$)$ It modifies the engine's firing order.

$-$ C$)$ It influences torsional vibrations.

$-$ D$)$ It impacts the secondary balance.

$8.$ The choice of firing order in radial engines primarily influences which aspect of engine operation?

$-$ A$)$ Thermal efficiency

$-$ B$)$ Aerodynamic drag

$-$ C$)$ Mechanical balance

$-$ D$)$ Fuel distribution