In which one of the following conditions, can an agent sub-delegate his authority to another person?

As per the Indian Contract Act, 1872, an agent is generally not allowed to delegate his authority to another person unless certain exceptions apply.

Sub-delegation is permissible in the following cases:

1. When commercial practice involves such delegation: If it is a common trade custom or practice in a particular business, an agent can delegate authority. (Option D)

2. When the principal expressly allows delegation: If the principal has given permission, the agent can appoint a sub-agent.

3. When the nature of work requires delegation: If the duties assigned are such that they require another person’s involvement, delegation is allowed.

4. When unforeseen circumstances arise: In emergencies where the agent cannot perform duties, sub-delegation may be justified.

Options A, B, and C do not justify sub-delegation as per legal principles. Therefore, Option D is the correct answer.