Given the signature: O = {a}, F = {f}, P = {p} and V = {X}, specify which of the following are terms, atoms, literals, or none. PLEASE EXPLAIN YOUR ANSWER.

(a) a.

(b)a

(c) X

(d) Y

(e) f(X)

(f) f(f(X))

(g) p(a)

(h) p(a)

(i)p(a).