4.2 × 4.2 - 1.9 × 1.92.3 × 6.1 is equal to:

Answer: Option B

$$\begin{array}{rl}& \text{Let }a=4.2\text{ and }b=1.9\\ & \text{Given Expression}\\ & =\frac{a^2-b^2}{\left(a+b\right)\left(a-b\right)}\\ & =\frac{a^2-b^2}{a^2-b^2}\\ & =1\end{array}$$