A box contains 20 electric bulbs, out of which 4 are defective. Two bulbs are chosen at random form this box. The probability that at least one of these is defective is:	Choose the correct answer
A) 8 / 19 B) 7 / 19 C) 10 / 19 D) 20 / 19 E) 22 / 19

Rationale: "p ( none is defective ) = 16 c 2 / 20 c 2 = 12 / 19 p ( at least one is defective ) = 1 - 12 / 19 = 7 / 19 answer b"
Answer: B