Two students are assigned a census in a town of 200 people to determine how many pairs of shoes each person owns. Neither student completes the census. Bill surveys 40 people, while Carmen surveys 150. While both get a mean of 4.5 pairs of shoes, Bill records an inter-quartile range of 2.0 and Carmen gets an inter-quartile range of 5.5. Carmen's data is more accurate because

A) her mean is higher.
B) her sample was larger.
C) it has a lower variation.
D) it has a higher variation.