As a fitness enthusiast you have tried everything from spin class to CrossFit, and you have learned the most effective ways for individuals to get results. You may want to inquire about the goal of the exercise before answering the question, as everyone has different purposes for working out. Here's an example answer:

"It depends on my client's fitness goals. If they are trying to lose weight I recommend high intensity interval training (HIIT). If they are older or have previous injuries I would recommend swimming, cycling, or aerobics. Zumba is a great option as well. It really depends on my client's needs and goals."

This response shows that you take into account that everyone's body is different and depending on what you are trying to accomplish through exercise, you may need something different.