Final answer:
Option (A), The presence of termite pellets is the best evidence of a drywood termite infestation. Termites digest wood by relying on symbiotic microorganisms in their guts that produce necessary enzymes for breaking down cellulose and lignin.
Step-by-step explanation:
The best evidence of a drywood termite infestation is the presence of termite pellets (fecal pellets). Termites are able to digest wood thanks to a mutualistic relationship with symbiotic protozoa and archaea that live in their guts.
These microorganisms produce enzymes that break down cellulose and lignin in the wood, providing nutrients that can be utilized by the termite. This process allows termites to thrive on a diet that is mainly wood despite their inability to produce lignin-decomposing enzymes themselves.