Answer: The correct answer is- B) bacteria, C) Earthworm, and D) Humus.
Out of the given options, bacteria, Earthworms, and Humus helps in improving the fertility of soil.
Bacteria and Earthworms can decompose the organic matter and convert it into usable form for plant's growth. They also help in enhancing the amount of air and water in the soil so that it can be efficiently utilized by plants.
Humus is an organic material that is dark in color and rich in nutrients as it is obtained by the decay of plant and animal matter. It helps in sustaining moisture in the soil and by providing nutrients, it makes the soil fertile.
Thus, B), C), and D) is the right answer.
