Velocity of sound increases on a cloudy day. why?

Because there's a decrease in density.

Explanation:

For fluids, the speed of sound (Vs) is given by the relationship :

, where:

Ks = coefficient of stiffness, the isentropic bulk modulus (or the modulus of bulk elasticity for gases).

d = density of the fluid.

As we can see, speed of sound is inversely proportional to density. If density decreases, speed of sound increases.

In a cloudy day, humidity is very high (in fact, when it rains, relative humidity is 100% (maximum) which is why the clouds can't hold any more water). Density is inversely proportional to humidity. So, in a cloudy (or highly humid) day, density decreases, causing an increment in the velocity of sound.

we need some answer choices, or something like that

explanation:

i guess that visual aids present persuasive examples to what you are presenting, some factors would be theme (does it fit with the color, information, what you are presenting), size (can you see it, is it a big enough span of data/information), and overall look of the visual aid.

hope this : )