Newton-Pepys Probability Problem

Problem
Samuel Pepys wrote Isaac Newton to ask which of three events is more likely: that a person get (a) at least 1 six when 6 dice are rolled (b) at least two sixes when 12 dice are rolled, or (c) at least 3 sixes when 18 dice are rolled. What is the answer?

A. (a) is more likely than (b) and (c)
B. (b) is more likely than (a) and (c)
C. (c) is more likely than (a) and (b)
D. (a), (b), and (c) are equally likely