__________ and ________ are stimulus preference assessment methods, while ________ and __________ are reinforcer assessment methods.

A. Free-operant, trial-based; concurrent schedules, multiple schedules
B. Concurrent schedules, progressive ratio schedules; free-operant, trial-based
C. Asking, progressive ratio schedules; trial assessment, multiple observation
D. Multiple operants, free-choice; tandem schedule, multiple schedule