A histogram titled Greeting card sales has date on the x-axis and cards (millions) on the y-axis. January is 1 card, February: 11, March: 1, April: 1, May: 9, June: 7, July: 1, August: 1, September: 1, October: 9, November: 7, December: 12. The histogram shows the monthly sales for a greeting card company in one year. Which best describes the data for May–June and October–December? clusters no frequency gaps symmetry