Hi The answe choice is 5 correctly.
Here is the logic
A) Play performed for charity
Let A be the set of people who wants to buy tickets for charity
Let B be the set of people who never seen the play, from the statement A is a subset of B.
Hence the demand is very high, they decided to sell tickets only to people who have never seen the play ( that is to B) , doing so satisfies the condition that all who wanted to buy tickets for charity actually did buy ticket which means set B and set A are equal which was exhibited by statement 5