The displacement of particles in a string stretched in the x-direction is represented by y. Among the following expressions for y, those describing wave motion are:

Explanation

The correct expression for wave motion is typically of the form y(x, t) = A sin(kx - ωt) or y(x, t) = A cos(kx - ωt), where A is the amplitude, k is the wave number, and ω is the angular frequency. Option A, cos kx sin ωt, follows this form, as it is a combination of spatial and temporal sinusoidal functions, representing a wave traveling through space. Option B is a quadratic expression and not sinusoidal, which is essential for wave representation. Option C involves a squared trigonometric function, which does not describe a simple harmonic wave. Option D involves a cosine function of a quadratic expression, deviating from the linear form required for wave motion.