Which one of the following element is not essential for plant growth?

Correct option is B

Sodium (Na) is not considered an essential element for plant growth. While some plants may tolerate or even utilize small amounts of sodium, it is not required for the general growth and development of plants like other essential elements (such as Nickel, Manganese, and Zinc). Sodium is primarily a non-essential trace element and is generally harmful to most plants in excess.