短文改错。

      Yesterday a school boy is daydreaming in class.Not knowing that he was doing,he put a pen

cap into his mouth.A few minutes late,he was terrified to find that he had swallowed it!The teacher

was shocking when the boy stood up and said,"I've just swallowed a pen cap."He was quickly

sent the nearest hospital.There a doctor examined his and said the best treatment was to take

some medicines so that the pen cap could pass natural.Three hours later the boy successfully

made it."She is really lucky," said the doctor."It's not rare that small children put things into their

mouths for a fun.It's very danger."

就强度大小而言，岩石的强度常常______岩体的强度。