Roots of a plant in hydroponics are submerged in a solution of dissolved

The correct option is fertilizers.

Hydroponics is a modern method of growing plants without using soil. In traditional farming, plants extract essential nutrients, minerals, and water from the ground. In a hydroponic setup, soil is completely eliminated, and the plant roots are instead suspended or supported in an inert medium and submerged in a water-based solution.
To support plant growth and survival in the absence of soil, a complete set of nutrients must be supplied directly to the water. This is achieved by dissolving specially formulated hydroponic fertilizers in the water. These fertilizers contain all the essential macronutrients (like nitrogen, phosphorus, potassium, calcium, and magnesium) and micronutrients (like iron, manganese, and zinc) that the plant needs in a highly bioavailable form.

Consequently, the roots of a plant in a hydroponic system are submerged in a solution of dissolved fertilizers, allowing them to absorb nutrients directly and efficiently.