To receive marketing emails from a company, a person must sign up via a form...

A single opt-in process is when a person fills out a form and is automatically added to the mailing list without any further confirmation1.

An automatic opt-in process is when a person is added to the mailing list without their explicit consent, such as by pre-checking a box or by purchasing a product2.

A double opt-in process is when a person fills out a form and is then sent an email that requires a click to confirm the opt-in. This ensures that the person has given their permission and has a valid email address13.

Therefore, the correct answer is C. Double opt-in, as it matches the description of the scenario given in the question. References:

1: How to Set Up Double Opt-In (COI) - Marketo

2: Opt-In Email Marketing Benefits and Best Practices for 2024

3: Double opt in process - Marketing Nation