阅读下列短文，从每题所给的A、B、C、D四个选项中选出最佳选项。
A
Discover the Huge Health Benefits of Strength Training
One of the best ways to stay fit and healthy as you age is to do strength and power training exercises．It is known that when you are in your thirties, you will begin to lose muscle mass．This loss actually contributes to achy joints, the increased risk of injury, and the“middle-age spread” we all fear．What’s more, the older you get, the faster muscle mass loses．It means that eventually, simple tasks like getting out of a chair and climbing stairs can become more difficult．
Strength training can help you build muscles, make you strong, increase your staying power and make everyday activities easier．By combining strength and power training exercises, you’ll not only get stronger, but also improve your reaction speed．As you grow older, that’s critical because it can help prevent falls．Here is a book, Strength and Power Training for All Ages, for your reference．
Common sense about fitness in the book:
·The key muscles to work for an injury-free body
·How to tell how much weight is suitable for you
·How to strengthen the bones most likely to break
·How to take pressure off your knees when walking or running
·Why you’ll want to apply heat to sore joints before you exercise
Four total body workouts in the book:
·Build bones
·Fight diseases
·Improve balance
·Strengthen muscles &Increase muscle power
Get a copy, start training, and then you’ll discover a whole new self．
21．What will happen as people age according to paragraph 1?
A．They will need less exercise．
B．They will improve reaction speed．
C．They will experience muscle loss．
D．They will have better staying power．
22．What does Strength and Power Training for All Ages mainly teach people to do?
A．Train their brains． B．Build a sound body．
C．Treat bone diseases． D．Cut down their weight．
23．What is the text?
A．A notice． B．An oral folktale．
C．A scientific paper． D．An advertisement．
