Correct option is C
The formula for the area of a rhombus is:
Area=12×(product of the lengths of its two diagonals)\text{Area} = \frac{1}{2} \times (\text{product of the lengths of its two diagonals})Area=21×(product of the lengths of its two diagonals)
So the correct option is:
(C) 12×(product of the lengths of its two diagonals)\frac{1}{2} \times \text{(product of the lengths of its two diagonals)}21×(product of the lengths of its two diagonals)