Three numbers are chosen from 1 to 20. The probability that they are not consecutive is

3 numbers can be chosen out of 20 in ²⁰C₃ ways.

As we have to choose 3 consecutive numbers. So we can’t choose 19 and 18.

Choosing consecutive number is same as choosing a single number because other 2 numbers are automatically chosen.

This can be chosen 18 ways.

∴ P(chosen numbers are consecutive) =

Our answer matches with option (d)

∴ Option (d) is the only correct choice