Final answer:
Clear instructions and positioning aids can be used to prevent voluntary motion.
Step-by-step explanation:
The correct answer is b. 1 and 2 only. Clear instructions and positioning aids can be used to prevent voluntary motion. Clear instructions ensure that the person performing the task understands what needs to be done and can follow the instructions accurately, reducing the chances of any voluntary motions. Positioning aids, such as braces or splints, can provide support and stability, preventing involuntary motion.
On the other hand, a correct pre-exposure routine (option 3) does not necessarily prevent voluntary motion. It refers to the steps taken before exposure to a certain situation, but it may not directly address preventing voluntary motion.