When you get a vaccine it injects a controlled amount of the illness into you, so the immune system can build up an immunity. The memory cells come into play when the illness comes back.
Answer: Option B
Explanation:
Cheerleading requires stamina for a longer period of time. This activity requires more energy and one who is training for cheerleading needs to get training for working on her body.
Rae is getting training for this activity as she has started 45 minutes roller blading for enhancing her endurance.
After rollerblading her heart rate is 128 beats per minute but she wants a heart beat of 140-170 beats per minute. For this she should skate on the hills in the park to get more strength and increase the cardio respiratory process.
