Which sentence is an example of a pun

Host danny boyle used a line from what shakespearean play to welcome the athletes and fans arriving in london for the 2012 olympics?

Respiration involves the breakdown of sugar. this process results in the production of energy for the cell. i'm order for cells to produce the most energy, what gas should be present?

Ten students compared the amount (in dollars) they spent on books each week. the box plot shows the results. the median amout they spent each week is . the difference of the first and third quartiles of the data set is?