To find out how many 9's are used in the numbers from 1 to 100, we need to consider each digit position separately.

1. For the units digit: Out of the numbers from 1 to 100, 9 is used as the units digit in 9, 19, 29, ..., 99. So, there are 10 numbers where 9 is used as the units digit.

2. For the tens digit: Out of the numbers from 1 to 100, 9 is used as the tens digit only in 90, 91, 92, ..., 99. So, there are 10 numbers where 9 is used as the tens digit.

Therefore, the total number of 9's used in the numbers from 1 to 100 is 10 + 10 = 20.

Hence, the correct answer is option D) 20.

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