A prefix penta is used in naming the complex 

Given:

A prefix Penta is used in naming the complex.

Explanation:

Rule 1: Regardless of whether the complexion of a coordination molecule is cation or anion, the cation is always identified before the anion.

Rule 2: If a coordination complex has more than one kind of ligand, the names of the ligands must be listed in alphabetical order, followed by the name of the central metal atom or ion.

Anionic ligand names end in O.

The usual nomenclature is used for neutral ligands.

Rule 3: The phrases bis, tris, and tetrakis are used and the ligand they refer to is given in parenthesis if the name of the ligand already has a numerical prefix.

Rule 4: Write the name of the central metal atom or ion after identifying the ligand in alphabetical order.

The Latin name of the metal ends in the suffix -ate if the complex is an anion.

Rule 5: In parenthesis, a Roman numeral designating the metal's oxidation state is supplied.

Rule 6: The nomenclature of the neutral complex molecule resembles that of the complex cation.

Rule 7: These ligands may be affixed to the principal metal.

Hence, the correct answer is (B). ${\mathrm{CrCl}}_3.5{\mathrm{NH}}_3$