Superposition of two equal-frequency waves traveling in opposite directions produces stationary (standing) waves.

The highest point of a wave above mean level is called the crest, so option A is correct.

Transverse waves require shear elasticity which solids possess, whereas liquids and gases cannot support shear stress to sustain transverse waves.

Standing waves on a string occur when the string length is an integral multiple of half wavelengths, so 'Half' is correct.

Elastic potential U = 1/2 k x^2 = 0.5×175×0.7^2 = 0.5×175×0.49 ≈ 42.9 J.

Frictional (dissipative) forces remove energy from oscillatory systems, causing damping so they do not oscillate indefinitely.

A seconds pendulum has period 2 s, so its frequency is 1/2 = 0.5 Hz.

Resultant amplitude = √(3^2 + 4^2) = 5 cm, so option C is correct.

λ = 1 cm = 0.01 m, period T = 2 s, so v = λ/T = 0.01/2 = 0.005 m/s.

T = 2π√(m/k) = 2π√(2/200) = 2π×0.1 ≈ 0.628 s, i.e., 0.63 s.