Which mineral is present in milk?

Ammonium sulphate is:

Which of the following organisms does not fix $N_2$?

Identify the mismatched pair.

Which of the following statements are true? If false,correct them:
$(a)$ Boron deficiency leads to stout axis.
$(b)$ Every mineral element that is present in a cell is needed by the cell.
$(c)$ Nitrogen as a nutrient element,is highly immobile in the plants.
$(d)$ It is very easy to establish the essentiality of micronutrients because they are required only in trace quantities.

Which of the following statements is incorrect?