Answer:
Hold breath during sets
Step-by-step explanation:
Weight training can be classified into three types of exercises: free weighs, body-weight exercises and machines.
Free weights refer to exercises with barbells, dumbbells, or any other object that can be free-moved. This type of exercises improve resistance, during these type of exercises is important to hold breath, due to the pressure applied by weights.
Therefore, the right answer is the third option. Other option are not useful in this context.