Which of the following groups of animals you would expect to evolve chemical defences against predators?
A. slow moving with hard shell.
B. sedentary without a hard shell.
C. burrowing.
D. arboreal.

The correct answer is B. Sedentary without a hard shell because in other cases as given in the options evolving a chemical defence system is unnecessary, of course there are exceptions but a sedentary being without hard shells is likely to evolve chemical defences like Calotropis.