The $HCF$ of $25$ and $52$ is $1$.

Which of the following is not a polynomial in variable $x$?

If the Least Common Multiple $(LCM)$ of two numbers is equal to their product,then their Greatest Common Divisor $(GCD)$ is ........ .

The last digit of $2^{m} \cdot 5^{n}$ (where $m, n \in N$) is . . . . . . .

From the given factor tree, find the values of $x$ and $y$ respectively.

The Greatest Common Divisor $(GCD)$ of $13, 23,$ and $31$ is .......