A) Humus has many negative charges and is able to bind to positively charged potassium.
The correct answer is A. Humus, which is a dark, organic component of soil, has a high concentration of negatively charged particles. Potassium, on the other hand, carries a positive charge. Due to these opposite charges, humus is able to bind to and retain potassium in the soil, preventing it from being washed away through leaching. This helps to ensure that the potassium remains available for plant uptake and utilization, promoting healthy plant growth and reducing the loss of this essential nutrient.