Answer:
Option C. hydroxide ions (OH-).
Explanation:
A base is a substance which dissolves in water to produce hydroxide ion (OH-) as the only negative ion. It therefore means that a base contains more hydroxide ions (OH-).
Cadium
Down a period, atomic radii decrease from left to right due to the increase in the number of protons and electrons across a period.
Molality is defined as 1 mole of a solute in 1 kg of solvent.
Molality=

Number of moles of solute, n=

Given mass of the nitrobenzene=0.2 g
Molar mass of the substance= 123.06 g mol⁻¹
Number of moles of nitrobenzene,

Number of moles of nitrobenzene, n= 0.0016 mol
Mass of 10.9 g of naphthalene in kg=0.0109

Molality= 0.146 m
Try to understand all the rules and laws like:
Aufbau Principle
Hund's rule
Pauli exclusion principle...
Then, you should understand the way in which you can fill the electrons in the orbitals!!