Final answer:
The type of complement activation that requires the presence of antibodies is the classical pathway.
Step-by-step explanation:
The type of complement activation that requires the presence of antibodies is the classical pathway. In this pathway, antibodies recognize and bind to antigens on the surface of a pathogen. This binding then triggers a series of events that lead to the activation of complement proteins and the formation of destructive pores in the pathogen's membrane.
For example, when C1 binds to an antigen-antibody complex on an invading pathogen, it causes complement components C2 and C4 to split in two, initiating the classical pathway.
The alternate pathway, on the other hand, does not require antibodies for activation. Instead, it is triggered by the spontaneous breakdown of C3 convertase.