Change the decimal to a fraction: 0.123123123….

A. 12 13/10

B. 1 23/100

C. 123/999

D. 123/1000

E. This decimal is irrational and cannot be written as a fraction

To convert the repeating decimal 0.123123123... to a fraction, let's call it x:

- Multiply x by 1000 to shift the decimal three places to the right:
1000x = 123.123123123...

- Subtract x from 1000x to eliminate the repeating part:
1000x - x = 123.123123123... - 0.123123123...
999x = 123

Hence, the fraction equivalent of the decimal 0.123123123... is 123/999.

Therefore, the correct answer is C. 123/999.