Answer:
A) +/+
Step-by-step explanation:
The form of interaction that exist between cellulose-digesting organisms in the gut of a termite and the termite itself is a +/+ interaction.
This is because the interaction of both organisms is beneficial to each of them. While the cellulose-digesting organisms are able to get their shelter in the gut of the termite, the termite benefits from the presence of these cellulose-digesting organisms by getting their cellulose-containing food materials digested by them.
Hence, it is a mutually beneficial interaction.
Option A is the correct option.