Which of the following is the output of $545\times 545-125\times 125$?

The given expression is of the form $a^2-b^2$, where $a=545$ and $b=125$.
We can use the algebraic identity:

$$a^2-b^2=(a-b)(a+b)$$

Substitute the values:

$$545^2-125^2=(545-125)(545+125)$$

$$545-125=420$$

$$545+125=670$$

Now multiply the results:

$$420\times 670=281400$$