Final answer:
Carpenter Ants protect Woolly Aphids to maintain a mutualistic relationship where they benefit from the honeydew that aphids excrete, offering protection in exchange.
Step-by-step explanation:
Carpenter Ants protect Woolly Aphids because they have a symbiotic mutualistic relationship. The aphids consume plant phloem sap and excrete a sugary substance called 'honeydew' or 'frass', which the ants collect and feed to their colony. In return for this rich food source, the ants defend the aphids from predators, effectively providing them with protection. This biological interaction is an example of an ecological partnership where both species benefit, similar to other symbiotic relationships found in nature, such as leaf-cutter ants farming fungi or Basidiomycota fungi protecting scale insects.