Which elements are considered as balancing elements?
A. Ca and K
B. C and H
C. N and S
D. Mg and Fe

Hint:The balancing elements are those mineral elements that help to overcome the toxic or poisonous effects of other elements.
It includes calcium, magnesium, and potassium and they have counteracted against manganese, nickel, zinc, boron, copper, and lead.

Complete answer: An element is a substance that cannot be broken down into any other substance.
There are hundreds of elements, each having its own type of atom.
Everything in this world and universe consists of atoms of at least one or more elements.
Based on the mobility in the phloem, elements are also classified into three main types:
1. Mobile elements: It includes Nitrogen, potassium and etc.
2. Immobile elements: It include Calcium, Iron, and Boron
3. Intermediate: It includes Zinc, Manganese, and copper.
Functions of elements
Protoplasmic elements: N, P, S
Balancing elements: Ca, Mg, K – counteract toxic effects of other minerals by causing ionic balance.
Framework elements: C, H2O – as they are the constituents of carbohydrates that form cell walls.
Catalytic elements: Mn, Cu, Mg, etc.

So, the correct option is option A. Ca and K.

Note: Calcium is very important in cell membranes and is very helpful in the growing parts of plant roots and tops and the deficiency of calcium causes them to wither and die.
Calcium is an essential plant nutrient.
It is required for different structural roles in the cell wall and membranes, it is a counter‐cation for inorganic and organic anions in the vacuole.
It is found in most types of soils and is made available to plants through the weathering of minerals.
As an alkaline earth metal, calcium plays a major role in controlling soil pH (potential of hydrogen), a measure of the soil's acidity or alkalinity.