Question

in a transverse wave, particles move:

in circles

in the same direction as the wave

perpendicular to the direction of the wave

only in liquids

Explanation:

In a transverse wave, the motion of the particles is perpendicular to the direction of wave propagation. For example, in a wave on a string, the string moves up and down (perpendicular) while the wave moves along the length of the string. Particles moving in circles is characteristic of surface water waves (a combination of transverse and longitudinal motion in some sense but not pure transverse). Particles moving in the same direction as the wave is for longitudinal waves (like sound in air). And transverse waves can exist in solids (e.g., wave on a metal rod) not just liquids.

Answer:

Perpendicular to the direction of the wave