Using a calculator,
n C r = 49 C 6 = (49!)/(6!*(49-6)!) = 13,983,816
Which tells us the number possible combos we can have of six values (out of a pool of 49)
There's only one way to win the lotto. This is because order doesn't matter. As long as you have all of the the six values in any order, then you've won.
So we divide the number of ways to win (1) over the total number of ways to play (13,983,816) and we get:
1/13983816 = 0.0000 0007 15 = 7.15*10^(-8)
Answer: Choice D
note: I used a few spaces for the long decimal value shown above to make the number a bit more readable