6 DO
Which are examples of a medium?
water and air
amplitude and wavelength
crests and troughs
compressions and rarefactions

water and air

Explanation:

The examples of medium from this problem is water and air.

A medium is an agency or a means of propagating energy, waves or even facilitating a chemical reaction.

Fluids are very good medium in chemistry for chemical reactions. The two most common media used are air and water.

In physics, a vacuum is an empty space that has been evacuated. It also serves as a medium to study some physical phenomenon.

d is

the number of protons in the nucleus of a given element. has slight luster and conducts electricity at high temperatures like metal.but like a nonmetal,boron is brittle and does not conduct electricity well at low temperatures. in graphite, carbon is a soft,brittle solid.it is reflective,ductile,or malleable.