When Helle was born, her parents agreed to allow her to participate in a research project that investigates the development of motor skills in children. Every year, Helle's parents complete a survey answering questions about how Helle's motor skills have changed. The researchers are using only one group of parents and children for the study. Helle and her parents are participating in a study that uses a _____ design.

• A. longitudinal
• B. cross-sectional
• C. cross-sequential
• D. combination of cross-sectional and cross-sequential