The correct conclusion about the interquartile range of Jenny’s box plot would be:
C The middle 50% of the dogs weighed between 5 and 15 pounds.
This option specifically addresses the interquartile range, which represents the range within which the middle 50% of the data lies. Options A, B, and E make general statements about the weights that do not specifically relate to the interquartile range, while option D incorrectly associates an individual dog's weight with an improper influence on the interquartile range.