What purpose do neutrons serve in the nucleus ? What happens if there are too many or too few neutrons?

These nuclei with different numbers of neurons are called isotopes

neutrons' main function is to attract each other and keep the nucleus of an atom intact. a nucleus will become unstable if there are too many or too few neutrons in it.

Explanation:

too many= it will undergo beta decay (the neutrons will changes into proton)

too few= there will be an imbalance between forces which leads to nuclear imbalance

the best answer is d because the strong cohesion is caused by the ability of water molecules to undergo hydrogen bonding.

a is incorrect because when water solidifies, it becomes   ice, which expands and occupies a bigger volume for the same mass of water in its liquid state.

b is incorrect because water has high surface tension. besides bonding to itself it hydrogen bonds to other molecules at the top decreasing possibility for breaking of attractive forces.

c is incorrect because the water molecule has oxygen which is highly electronegative and so pulls the electron pair towards itself creating a dipole moment, making the molecule polar.

e is incorrect because water has strong adhesion, ability to stick to other molecules such as glass because of this molecules having stronger hydrogen bonding than water.