Which skill is needed to build an efficient solution?

A customer frequently holds seminars and other events to interface with their customers.

They plan to do the following:

– Use SmartCapture forms to write data into event registration data extensions.

– Cross-reference the records in each registration data extension with corresponding invitation email sends.

– Send a follow-up email to customers who click on the registration link in the invitation email, but do not complete registration.

Which skill is needed to build an efficient solution?
A . AMPscript
B . SQL
C . HTML
D . CSS