Passage Two
We think of aerobics as being a high impact activity but actually [29]aerobic exercise by definition means we practice the same large muscle group, rhythmically, for a period of 15 to 20 minutes or longer while maintaining 60-80% of your maximum heart rate. Think of aerobic activity as being long in duration yet low in intensity. [30]You should be able to carry on a short conversation while doing aerobic exercise. Aerobic exercise conditions the heart and lungs by increasing the oxygen available to the body and by enabling the heart to use oxygen more efficiently. The aerobic curve occurs when you begin exercising, increase your intensity level, hit the high point and gradually decrease your intensity level. [31]The goal when exercising aerobically is to hit your target heart rate and maintain it for the entire exercise session. This works the heart muscle more effectively and burns more calories. You start, hit your target zone, then you maintain your pace until the cool down. As your heart becomes conditioned, you will have to work harder to reach the target zone. [32]If you are too tired to continue exercising in an aerobic class, march in place for a while until you can resume exercising. It is not OK to stop in the middle of an aerobic class because your body is sending extra blood to the muscles. Stopping suddenly can lead to muscle cramping and dizziness.

Questions 29 to 32 are based on the passage you have just heard.
29. What do we know about aerobics from the passage?
正確答案：B
解析：文章開篇就介紹了什么是有氧運動，B與此一致。
30. What will happen when we are doing aerobic exercises?
正確答案：B
解析：短文談到，在做有氧運動時你應該能夠進行短時間的談話，故選B。
31. What is the goal of aerobics according to the speaker?
正確答案：B
解析：短文談到，有氧運動的目標就是在運動的全過程保持目標心跳率，故選B。
32. What does the speaker suggest we do when we are tired in an aerobic class?
正確答案：C
解析：短文談到，如果你在有氧課里太累了以致于無法繼續鍛煉，那就原地踏步一會兒直到你可以恢復鍛煉為止，故選C。