Student: A box contains nine bulbs out of which 4 are defective. If four bulbs are chosen at random, find the probability that all the four bulbs are defective.
Options:
(A) 62/63
(B) 125/126
(C) 1/63
(D) 1/42
(E) 1/126.
Another student: Let's say, hmmm...
Answer: Option E
Out of nine, five are good and four are defective. Required probability = c/c = 1/126 Final answer: (E).