请教一道Prep模考题,谢谢了！！！

macli

A contest will consist of n questions, each of which is to be answered either True or False. Anyone who answers all n questions correctly will be a winner. What is the least value of n for which the probability is less than 1/1000 that a person who randomly guesses the answer to each question will be a winner?
答案有：5; 10; 50; 100; 1000

正确答案: 10

leeqii

(1/2)^n<1/1000
解出n即可~~n最小为10