Which of the following is not equal to 1?

Let us solve each option,

For option A,

For option B,

Again we have another law of indices which is as follows:

a^m ÷ aⁿ = a ^(m-n)

According to Law of indices,

a^m × aⁿ = a ^{(m + n)}

For option C,

For Option D,

So the correct answer is D.