You are asked a question and you don't have a clue about it. But, luckily you are given $K$ ($K \ge 4$) possible answers and only one is the right one. Because you choose your answer randomly you would like to increase your chance of answering the question right. You have two options:
- Choose an answer randomly.
- Choose an answer randomly, exclude it and then choose another answer randomly from the other $K-1$ given answers.
So the question, would you have better chance if you choose option 2 than option 1? And if it's better, how many times would be the best option, and stopping before it become a bad idea (excluding large part of the answers).
Let's say. $K=4$. Then you'll have $25$% odds choosing the right answer with option 1.
If you exclude that answer you have $33$% or $0$% odds of choosing the right answer.