The correct option is
D Ammonotelic when plenty of water is available.
An ammonotelic organism excretes nitrogenous waste as soluble ammonia. Class Oligochaeta includes terrestrial earthworms and some other species that live in freshwater. Aquatic oligochaetes excrete ammonia while terrestrial oligochaetes excrete urea but Lumbricus produces both ammonia and urea.
So, the correct answer is 'Ammonotelic when plenty of water is available.'.