The correct option is D 42
To find the least common multiple, first let's list down the multiples of 6 and 7.
Multiples of 6 = 6, 12, 18, 24, 30, 36, 42, 48.......
Multiples of 7 = 7, 14, 21, 28, 35, 42, 49.........
We can clearly observe that 42 is lowest common multiple.