How does the idea of a neutron help address the puzzles about the protons in the nucleus and the
mass of atoms?

The sum of the number of neutrons and protons gives the mass number.

Explanation:

n other words, when the number of neutrons is known and the atomic number of an element is known, it becomes easier to determine the approximate mass number by adding the two. Therefore, when the number of neutrons and protons are known, mass number is made the subject of the formula and get its value.

Generally,

Mass number = Number of protons + Number of neutrons.

Number of protons= Mass number - Number of neutrons

Number of neutrons = Mass number - Number of protons.

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.

b. accuracy of the data matters alot more than its number of digits, organization or amount of detail. quantitative observation is more accepted than the qualitative observation.