From the given food web, it is understandable that K is a producer, as it does not eats any plant or animal and all others are consumers. Let us discuss the options.
(i) This statement is incorrect as an omnivore eats both producers and consumers, but M does not eat producers.
(ii) This statement is also incorrect as N is not a prey as it is not eaten by anyone.
(iii) This statement is correct as K is a producer and without it all animals will die.
(iv) This statement is correct. We have to discuss about P's food habits.
P eats L. M also eats L. If there is no P, L population will increase. If L is increased, M will get more food to eat and will increase. Therefore, (iv) is correct.
(i) - Incorrect (ii) - Incorrect (iii) - Correct (iv) - Correct
Therefore Ans - B) iii and iv