For any positive integer $n$,the last digit of $5^n$ is always . . . . . . .

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

In the decimal representation of $\frac{7}{80}$,how many digits will be there after the decimal point?

The value of $\sqrt{1+1}$ is.......

Every composite number greater than $1$ can be expressed (factorized) as a product of primes,and this factorization is .........,apart from the order in which the prime factors occur.

For any positive integer $n$,the last digit of $5^n$ is always.......