(a) Till
(b) Muck
(c) Marl
(d) Peat
Ans. (c) : Marl

Explanation:-
Marl – It is a stiff marine calcareous clay of greenish colour.
Peat – It is the organic soil with fibrous aggregates formed from vegetable matter in excess moisture, highly compressible.
Muck – A mixture of fine particle, inorganic soil and black, decomposed organic matter.