Assertion (A): magnesium is not present in enamel of human teeth.
Reason (R ): Magnesium is an essential elements for biological functions of human beings.
A. Both A and R are true and R is the correct explanation of A
B. Both A and R are true but R is not a correct explanation of A
C. A is true but R is false
D. A is false but R is true
or (E) Both A and R are false.