A college teacher once gave a lively class to his students．

    He began by holding up a glass（1）　　 some water in it． He held it up for all to see， and asked the students， "（2）　　do you think this glass weighs？"

    "50g!" "100g!" "125g!" the students answered．

    "I really don't know unless I weigh it，" said the teacher， "but my（3）　　 is what would happen if I held it up like this for a few minutes？"

    "Nothing，" the students said．

    "OK． What would happen if I held it up like this for an hour？" the teacher asked．

    "Your arm would begin to（4）　　"said one of the students．

    "You are right． Now， what would happen if I held it up for a（5）　　？"

    "You might have muscles （肌肉） stress． You could（6）　　move the arm，" said another one．

    "You might have no （7）　　in the arm， or paralysis （瘫痪），"said a naughty student，"You （8）　　go to the hospital for sure!"

    "Very good． But during this period， did the weight of the glass（9）　　？" asked the teacher．

    "No，" the students said．

    "Then what（10）　　 the arm ache and the muscles stress？"

    The students were（11）　　．

    "No one knows？" the teacher asked， "Well， can you tell me how to（12）　　 it？'

    "Put the glass down!" said one of the students．

    "Exactly!" said the teacher．"The problems of life are something like this． Think of them for a few minutes in your（13）　　 and you seem OK． Think of them for a long time and you begin to hurt． Think of them even longer and you will not be able to do anything． It's important to think of the challenges in your life， （14）　　it's even more important to ‘put them down' at the end of every day before you go to sleep． That way， you are（15）　　﹣you wake up every day fresh and strong and can solve any problem that comes your way!"

（1）A． by	B． on	C． with	D． to
（2）A． how many	B． how much	C． how long	D． how far
（3）A． question	B． idea	C． answer	D． plan
（4）A． lose	B． die	C． stay	D． hurt
（5）A． day	B． summer	C． year	D． century
（6）A． hardly	B． quickly	C． widely	D． usually
（7）A． matter	B． problem	C． sense	D． secret
（8）A． needn't	B． can	C． shouldn't	D． must
（9）A． stop	B． happen	C． change	D． arrive
（10）A． sent	B． caused	C． tried	D． repeated
（11）A． in need	B． in silence	C． in danger	D． in time
（12）A． take off	B． hear from	C． deal with	D． get into
（13）A． arm	B． body	C． head	D． mouth
（14）A． but	B． and	C． so	D． or
（15）A． worried	B． lucky	C． nervous	D． relaxed