Final answer:
The correct answer for the recommended training variables for active stretching is C: 1 to 3 sets, holding each stretch for 1 to 2 seconds, with 5 to 10 repetitions.
Step-by-step explanation:
The recommended training variables for active stretching are typically C. 1 to 3 sets, hold each stretch for 1 to 2 seconds, and repeat for 5 to 10 repetitions. Active stretching involves contracting the muscle opposite to the one you're stretching, which helps to relax and stretch the targeted muscle. This type of stretching is dynamic, and the goal is to move through the stretch rather than holding it for a long period. Therefore, shorter holds and more repetitions are generally suggested to maximize effectiveness and safety.