Final answer:
The best option to increase dynamic range of motion of the hip flexors during resistance-based exercise is dynamic stretch.
Step-by-step explanation:
When seeking to increase dynamic range of motion of the hip flexors during resistance-based exercise, the best option is dynamic stretch. Dynamic stretches involve controlled movements that take muscles and joints through their full range of motion. For the hip flexors, dynamic exercises like leg swings or walking lunges can effectively increase flexibility and improve dynamic range of motion.