A searchlight on top of the watchtower makes 2 revolutions per minute. What is the probability that a man appearing near the tower will stay in the dark for at least 10 seconds?	Choices: A) 5 / 6 B) 3 / 4 C) 2 / 3 D) 1 / 2 E) 3 / 5

Rationale: "the searchlight completes one revolution every 30 seconds . the probability that the man ' s area will be lit up is 10 / 30 = 1 / 3 . the probability that he will stay in the dark is 1 - 1 / 3 = 2 / 3 the answer is c ."
Answer: C