Under which of the following categories is a partner of a partnership firm assessed?

Correct option is C

A partner of a partnership firm is assessed under the category of a "Firm". So the answer is (c) Firm. 
According to the Indian Partnership Act, the individuals who enter into a partnership are called "partners" individually, and collectively they are referred to as a "firm". 
Information Booster
· Taxation of a Partner:
· Salary, bonus, and commission received from the firm are taxed as business income.
· Share of profit from the firm is tax-exempt, as the firm itself pays tax on it.
Additional Knowledge
· Taxation of Partnership Firms:
· Partnership firms are taxed at a flat rate of 30% + surcharge and cess.
· Partners can claim deductions for interest and remuneration received from the firm.