填空题

Why do we cry Can you imagine a life without tears Not only do tears keep your eyes lubricated, they also contain a (36) that kills certain (37) so they can’t infect your eyes. Give up your tears, and you lose this on the spot defense. Nor would you want to give up the flood of (38) tears you produce when you get something physical or chemical in your eyes. Tears are very good at washing this (39) stuff out. Another thing you couldn’t do without your tears is cry from joy, anger, or sadness. Humans are the only animals that produce tears in response to (40) . And mot people say a good cry makes some feel better. Many scientists, therefore, believe that crying (41) helps us cope with the emotional situations. Tear (42) ,William Fred is trying to figure out how it happens. "One (43) ", he says, "is that tears discharge certain chemicals from your body". (44) , he says. If Fred is right, (45) Boys, for example, cry only about a quarter as often as girls once they reach their teenage years. And we all cry a lot less now than we did as babies. Could it possibly be that we face less stress (46) .