$7.$ What balancing technique is particularly effective for high$-$speed machinery with axial symmetry?

$-$ A$)$ Polar mass distribution

$-$ B$)$ Symmetric mass balancing

$-$ C$)$ Centrifugal balancing

$-$ D$)$ Radial array balancing

$8.$ In engines, how does counterweight placement affect torsional vibrations?

$-$ A$)$ It reduces torsional vibrations by adjusting rotational inertia

$-$ B$)$ It increases torsional vibrations by altering mass distribution

$-$ C$)$ It has no impact on torsional vibrations

$-$ D$)$ It indirectly increases torsional stiffness