Dr. Bloom wanted to learn if ice cream preferences were different at different stages of development. For her study, she conducted a one-time assessment in which she asked a group of 5-year-olds, a group of 15-year-olds, and a group of 30-year-olds to identify their ice cream preferences. Dr. Bloom conducted a _____.

A. case study
B. longitudinal study
C. cross-sequential study
D. cross-sectional study