Answer:
b. Phosphorous trichloride.
Step-by-step explanation:
The group of answer choices is showing us the systematic nomenclature, so let's remember the concept of systematic nomenclature: Systematic nomenclature indicates the atomicity (number of atoms) present in the molecules.
You can see that we have 1 atom of P (phosphorus), and 3 atoms of Cl (chlorine). The prefix to indicate that we have 3 atoms of a certain element is tri-, and this is a salt, so we the suffix goes to the nonmetal (in this case, Cl) and it would be -ide, so the correct name for PCl3 is phosphorous trichloride.
The answer would be b. phosphorous trichloride.