Identify a dark-coloured amorphous substance that is highly resistant to microbial action and undergoes decomposition at an extremely slow rate.

Humus

The correct answer is Option (2) –Humus

Humus is a dark-colored, amorphous substance that forms as a result of the decomposition of organic matter in soil. It is highly resistant to microbial action and undergoes decomposition at an extremely slow rate. Humus plays a crucial role in soil fertility by improving its structure, moisture retention, and nutrient-holding capacity. It also provides a habitat for beneficial soil organisms and helps in the retention of essential nutrients for plant growth.