PLEASE ANSWER

Which of the following statements about electromagnetic and mechanical waves is true?

A. Electromagnetic waves must travel through a medium, but mechanical waves do not require a medium.

B. Mechanical waves must travel through a medium, but electromagnetic waves do not require a medium.

C. Mechanical waves sometimes travel through a vacuum, and electromagnetic waves sometimes travel through matter.

D. Electromagnetic waves travel mostly through matter, and mechanical waves travel mostly through a vacuum.

B) Mechanical waves must travel through a medium, electromagnetic waves do not require a medium.

Explanation:

1). Mechanical waves:A mechanical wave is a wave that propagates through a material medium.As the wave travels through the medium,the particles that make up the medium must undergo displacements of various kinds, depending on the nature of the waves.They are of two types: a)Transverse wave

b)Longitudinal wave

a). Transverse waves:In transverse waves,the particle displacement is perpendicular to the direction of the wave propagation.This particles do not move along with the wave,they simply oscillate up and down about the individual position as the wave passes by.E.g,waves produced on a string.

b). Longitudinal waves:In a longitudinal wave,the particle displacement is parallel to the direction of the wave propagation.The particle oscillate back and forth about their equilibrium position.E.g, Sound wave in a gas.

2). Electromagnetic waves:This is a type of wave that require a physical medium for propagation and hence can travel through a vacuum.E.g,Light waves.

let that person have a turn to speak : )

the best answer is d because the strong cohesion is caused by the ability of water molecules to undergo hydrogen bonding.

a is incorrect because when water solidifies, it becomes   ice, which expands and occupies a bigger volume for the same mass of water in its liquid state.

b is incorrect because water has high surface tension. besides bonding to itself it hydrogen bonds to other molecules at the top decreasing possibility for breaking of attractive forces.

c is incorrect because the water molecule has oxygen which is highly electronegative and so pulls the electron pair towards itself creating a dipole moment, making the molecule polar.

e is incorrect because water has strong adhesion, ability to stick to other molecules such as glass because of this molecules having stronger hydrogen bonding than water.