Correct Option: A

As we know that when a number is divided by a, b or c leaving remainders p, q and r respectively such that the difference between divisor and remainder in each case is same i.e., (a – p) = (b – q) = (c – r) = t (say) then that (least) number must be in the form of (k – t), where k is LCM of a , b and c .
LCM of 15, 20 and 35 ( k ) = 420
Here , remainder = 8
∴ Required least number = 420 + 8 = 428