Any object struck at its natural frequency will vibrate violently. this is known as resonance. applications of this include earthquakes knocking down building and
a) rainbows created in air.
b) microwaves created in ovens.
c) light being created by the sun.
d) sound being created in music instruments.

option D)sound being created in music instruments

Explanation:

Resonance occurs when an object close in contact to a vibrating body begins to vibrate at the same frequency of the vibrating body.

Usually each object has a THRESHOLD frequency which must be equaled or exceeded before it is set into vibration.

Therefore, this is the PRINCIPLE behind MELODY i.e how sound is being created in music instruments.

they deliver oxygen to the blood

the relative standard reduction potential of the half-cell in which reduction occurs; more positive than the other half-cell. reduction is a chemical process in which electrons are added to an atom or an ion; it always occurs accompanied by oxidation of the reducing agent.