What is the primary content goal when a company publishes eBooks and webinars that require user sign-up?

The correct option is c).

When a company publishes eBooks and webinars that require user sign-up, their primary content goal is lead generation. This strategy involves collecting contact information from potential customers (leads) in exchange for valuable content, allowing the company to nurture these prospects for future sales.

The final answer is $\boxed{\text{c. Lead generation}}$.