You decide to ride your bike for 30 minutes, raising your heart rate to the middle of your target heart rate zone. what type of activity is this an example of?

aerobic, because it uses strong bursts of energy for a short duration
aerobic, because it uses oxygen for a long duration
anaerobic, because it uses oxygen for a long duration
anaerobic, because it uses strong bursts of energy for a short duration

Aerobic, because it uses oxygen for a long duration

Explanation:

Aerobic activities are related to the continuous use of oxygen from the air to provide energy to the muscles by working various muscle groups rhythmically,  in moderate or long periods of time.

Some examples of aerobic exercise are running, swimming, cycling (as the case described in the question) and dancing.

Anaerobic activities, in turn, are those that do not use oxygen as an energy source, exerting high power in specific muscle groups, in short periods of time, such as weight training, for example.

Aerobic because it uses oxygen for a long duration

Explanation:

Aerobic exercise (also known as cardio) is physical exercise of low to high intensity that depends primarily on the aerobic energy-generating process. This type of exercise is not in short bursts and uses energy for long periods of time. In this instance it is 30 minutes of time.