10 points and brainliest for the first to answer!

water is made up of two atoms and one atom.
a oxygen, hydrogen
b sodium, hydroxide
c hydrogen, oxygen
d carbon, oxygen

The nervous system interacts with the endocrine system by a. using hormones as connections b. sending nerve impulses directly to glands c. using neuroendocrine cells as connections d. sending neurotransmitters directly to neurons

Ialready know the answers to these questions and they are on the attachment. but i just need to know why that answer is the correct one. plz asap! this is for a report that i need to email by 10!

Which of the following types of stars are dim but can have high surface temperatures? giants main sequence stars supergiants dwarfs