NPK is an example of

The correct option is C

Fertilizer

The correct option is (C).

Explanation of correct option:

1. NPK means nitrogen, phosphorus, and potassium which are three very essential nutrients for the plants.
2. They are used as fertilizer which adds to the nutrition quality for plants.

Explanation of incorrect option:

Option (A):

1. Weedicides are chemicals that are sprayed in the crop fields and kill those weed plants.
2. These work very specifically and thus do not harm the crops we have planted in the field and selectively kill the weed.

Option (B):

1. Manure can be described as a nutrient-rich substance used for enhanced plant growth by farmers.
2. This is prepared very organically using everyday organic household waste that can include leftover food, vegetable, and fruit peel, newspaper, etc.
3. All these materials are dumped in a soil pit and left for soil microbes and worms to degrade them and thereby manure is formed.

Option (D):

1. Insecticides are chemicals that are used to kill the crop affecting insects.
2. These are sprayed in the crop fields and are designed to specifically kill only insects.

Final answer:

NPK is an example of fertilizer.