The answer is c and also have a nice day and do very good in school
To evaluate<span> an algebraic </span>expression<span>, you have to substitute a number for each variable and perform the arithmetic operations. In the example above, the variable x is equal to 6 since 6 + 6 = 12. If we know the value of our variables, we can replace the variables with their values and then </span>evaluate<span> the </span>expression<span>.</span>
The change of base rule says

If b = 1, then we will have


which is NOT possible. We cannot divide by zero. So this is why b = 1 is NOT allowed.