Sometimes people call each other  " scared cat" , but have you ever thought about this expression? When a cat is frightened, its heart starts beating faster, its muscles get tense, and there are changes in the chemicals in its blood-stream.  If the danger continues, this animal will do one of the two things. It will defend itself, or it will run away as fast as it can. Something like this also happens to people. When we are excited, angry, scared, or aroused by other emotions, our bodies go through many physical changes. Our hearts beat faster, and our muscles get tense. All of these changes make us more alert and ready to react. We, too, get ready to defend ourselves or run. Human beings, however, have a problem. If we give way to our feelings and let them take over, we can get into trouble. Have you ever said something in anger - and regretted later? Have you ever shouted at a teacher or told somebody you were lonely and then wished later you had kept your mouth shut? It isn't always wise to express your feelings freely. Does this mean that it's always smarter to hide our feelings? No! If you keep feelings like anger hidden away or bottled up inside, your body stays tense. Physical illnesses can develop, and you can feel disturbed badly inside. _ can actually be bad for your health. Feelings that you keep all bottled up inside don't just go away. It's as if you bought some bananas and stuck them in a cupboard. You might not be able to see them, but before long you'd smell them. And if you opened the cupboard, chances are you'd see little fruit flies hovering  all over them. They'd be rotten. You can try to treat emotions as if they were bananas in the cupboard. You can hide them and you can pretend they don't exit, but they'll still be around. And at last you'll have to deal with them, just like those bananas. According to the passage, human beings get into trouble because   _  .
they are not as alert as animals they always do something wrong to other people they sometimes can't control their feelings they don't pay attention to their physical changes