Arrange these statements in the correct sequence for the preparation of green manure.
$(a)$ Green plants are decomposed in the soil.
$(b)$ Green plants are cultivated for preparing manure or crop plant parts are used.
$(c)$ Plants are ploughed and mixed into the soil.
$(d)$ After decomposition,it becomes green manure.

• A
  $(c) \to (b) \to (a) \to (d)$
• B
  $(b) \to (c) \to (a) \to (d)$
• C
  $(b) \to (c) \to (d) \to (a)$
• D
  $(b) \to (d) \to (a) \to (c)$