Which Best Describes the Basic Premise of the Cross-Sectional Research

Which best describes the basic premise of the cross-sectional research design?

A) Assess different age groups (e.g., 5-, 10-, 15-year-olds) at same time (e.g., during same week)
B) Assess same age group (e.g., only 5-year-olds) at same time (e.g., during same week)
C) Assess different age groups (e.g., 5-, 10-, 15-year-olds) at different times (e.g., 5-year-olds in 2003, 10-year-olds in 2004, and 15-year-olds in 2005)
D) Assess same group (e.g., 5-year-olds) at different times (e.g., first test when kids are 5, then when they are 10, and finally when they turn 15)