The correct options are
B Clownfish being immune to the neurotoxin of Sea anemone
C Plants producing digestion-resistant seeds to ensure propagation even after getting eaten
Sea anemone produces a neurotoxin for the purpose of predation. As the sea anemone adapted to predation, clownfish coevolved with the sea anemone and developed mechanisms to stay safe of the neurotoxin. This enabled the clownfish to take refuge in the vicinity of deadly sea anemone. Many fruit-eating birds, especially in tropical rain forests are coevolving with the plants whose fruits they eat. The birds depend on these plants for nourishment, and in the process the plants get their digestion-resistant seeds dispersed by regurgitation or along with the birds' droppings. Giraffes having longer neck is a case of evolution.