At the bottom, deep bodies of water always measure 4°C, because at that temperature water has its highest [...] (fill in the physical quantity in question)

density

Explanation:

At the bottom, deep bodies of water always measure because at that temperature water has it highest density .

In water bodies like lake warm water rises up due to convection and at higher depths there is cold water, which is found to be at highest density of water.

When water molecules acquired heat energy  it become widely spread at the same volume and thus posses low density but at low temperature water molecule occupy less space therefore posses maximum density at

the electric field is a “force field” around a charged object that illustrates the direction the electric force would push an imaginary 

scattering of light by tiny particles in air to produce the colors we see on sky, is dependent on the following factors:

(i) wavelength of light

(ii) size of the scattering particle  

(iii) distance traveled by light through the atmosphere.

according to rayleigh's law of scattering, the amount of scattering is inversely proportional to the fourth power of its wavelength. shorter the wavelength, greater is its scattering. hence violet/blue light is scattered more than red.

sun's light is a composite light ( visible light) with wavelengths in the range 400 nm (violet) to 700 nm (red). as sunlight passes through our atmosphere, the molecules of air scatter light according to their wavelengths. during sunrise and sunset, the sun's position is below the horizon. hence light from the sun travels a greater distance in the atmosphere when compared to its position a noon.

as sunlight enters the earth's atmosphere, blue light is scattered away and at the end of its journey in the sky, only red and orange wavelengths remain in the beam.

hence at sunrise and sunset, the sky appears reddish orange.