Final answer:
The biotic factors in the habitat of termites living in dead trees are the termites and the protozoans that have a symbiotic relationship with them, which assists in cellulose digestion.
Step-by-step explanation:
In the habitat of termites living in dead trees partially buried under soil and stones, the biotic factors are the living components of the environment. Biotic factors would include Termites themselves and the protozoans that live in a mutualistic relationship with the termites, assisting them in digesting cellulose. Therefore, the correct answer to the question is C) Termites and protozoans.
It is important to note that other options such as the tree trunk, stones, soil, and humidity represent abiotic factors, which are the nonliving components of an environment like temperature and water. Abiotic factors do influence the living organisms, but they are not considered biotic.