Isn't this fascinating? For a cell to be able to divide, all of its DNA has to be replicated and then packaged as tightly condensed, duplicated chromosomes.
What does each duplicated chromosome have two of?
a) Copies of the entire DNA
b) Different chromatids, one from the father and the other from the mother
c) Identical chromatids
d) RNA molecules

cell regulation is conducted by special proteins.

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.

one part of the electromagnetic spectrum that arrives on earth as solar radiation from the sun is the visible spectrum. wavelengths of the visible spectrum combine to form what we refer to as

answer - d) ultraviolet radiation.

violet /   380–450 nm / 668–789 thz

violet is number 1 in the chart of visible light.