Which of the following is $NOT$ a criterion for the essentiality of a mineral element?

• A
  The element must be absolutely necessary for supporting normal growth and reproduction.
• B
  In the absence of the element,the plants do not complete their life cycle or set the seeds.
• C
  The deficiency of one element can be met by supplying some other element.
• D
  The element must be directly involved in the metabolism of the plant.