Which of the following is not a micronutrient?

If the daily requirement is more than 100 mg, they are called major elements or macrominerals. If the requirement of ceain minerals is less than 100 mg/day, they are known as minor elements or microminerals or trace elements, micronutrients. Options A and B are micronutrients. Option D : Boron is still regarded as a possibly essential element with no proved significance. Reference : D M Vasudevan , 6th edition page 411