In February 2010, Lydia Angyiou and her two sons were walking through their village in northern Canada. The sound of children shouting made her turn around. To her horror, Lydia saw a 700 – pound polar bear behind her eyeing her seven-year-old son．Getting between the bear and her child, Lydia yelled at the children to run away．She then began hitting and kicking the animal as hard as she could．A neighbor who heard all the noise came and shot the bear．But everyone agreed it was Lydia who had saved her children's lives．A local policeman described it this way: "I guess when your back is up against the wall, we come up with super-human strength."
Where does this "super-human strength" , courage and quick thinking come from? Experts say it comes from stress! In stressful situations, the body releases chemicals that prepare it to take action．These chemicals give people the speed and strength they need to fight danger or run away from it．
When we think of stress, we usually think of its negative effects．Studies, though, show that moderate levels of stress are actually helpful．In fact, the way we perform is usually affected by the amount of stress we feel．Stress causes the brain to release adrenaline （肾上腺素）which in turn increases our energy and excitement．The chemical gives us clearer minds and helps us to do more．This is why some people say they work better under a deadline．Adrenaline that is not released for long periods of time can cause us to be bored and lazy. So some stress actually increases and strengthens our abilities instead of weakening them. We sometimes turn out our very best work when we push ourselves to the limit．Stress can also make us more confident．Handling small amounts of stress now prepares us for handling serious situations in the future．Who knows? Today's stress may even prepare us for the next polar bear that comes along!
60．The author mentions the story of the mother and her children mainly to         .
A．tell people females also have enough strength to fight with a bear
B．show us how much the mother loves her children
C．set an example to us about how to deal with danger
D．illustrate to us stressful situations can make us stronger
61．What does the word “it” underlined in the second paragraph refer to?
A．released chemical               B．the body   
C．stress                  D．strength
62．What will the author probably continue to write in the paragraph that follows?
A．How to deal with a bear when you meet with it unfortunately.
B．Why we need small stress in life.
C．Tips for a person to develop his ability of dealing with stress.
D．When the brain releases adrenaline.