The correct option is C 341125
Since anyone's birthday can fall in one of 12 months, so total number of ways is 126.
`Now, any two months can be chosen in 12C2 ways. The six birthdays can fall in these two months in 26 ways. Out of these 26 way there are two ways when all the six birthdays fall in one month.
So, favourable number of ways is 12C2×(26−2).
Hence, required probability is
12C2×(26−2)126=12×11×(25−1)126=341125