What’s the answer because I have no clue

C. The number of protons.

Explanation:

All atoms of mercury will remain the same while different isotopes may have different number of neutrons.

For example, mercury has 80 protons, correlating with its atomic number. However, the number of protons, neutrons, and electrons could vary between each atom. If there are 80 protons, then there has to be 80 electrons. This means that the protons have to be the same in order to apply to all atoms of mercury

the answer is a. the yacht traveled from the dock north to the 200-meter marker in the bay in less than 5 minutes, giving the passengers several more hours to fish.

im doing peak rn so sry if its wrong