For small oscillations, the pendulum's period and frequency depend on its length and gravitational acceleration (g).

Wavelength = 50 cm / 25 = 2 cm; velocity = frequency × wavelength = 30 Hz × 2 cm = 60 cm s^-1.

The described lattice vibration quanta and inelastic scattering processes refer to phonons, so option C is correct.

Two close frequencies superpose to produce beats, a variation in amplitude at the beat frequency.

Uniform upward acceleration increases the effective gravitational acceleration, reducing the pendulum period (T ∝ 1/√g_eff).

Transverse waves are sustained in solids like strings, whereas in fluids (gases, liquids) transverse waves generally cannot propagate.

Anti-nodes are points of maximum displacement in a standing wave, so they have maximum amplitude.

At a node of a stationary wave, displacement is always zero and particles do not move, so particle velocity is zero.

For waves on a string or spring, increasing tension (e.g., stretching more) increases wave velocity.

Waves transmit energy and can also carry momentum; thus both energy and momentum (options B and C) are transferred.