16．
When the great library of Alexandria （亞歷山大圖書館） burned，the story goes，one book was saved．But it was not a valuable book； and so a poor man，who could read a little，bought it for very little money．
The book wasn't very interesting，but between its pages there was something very interesting indeed．It was a thin strip of animal skin on which was written the secret of the"Touchstone （試金石）"!The touchstone was a small pebble that could turn any common metal into pure gold．
The writing explained that it was lying among thousands and thousands of other pebbles that looked exactly like it．But the secret was this：The real stone would feel warm，while ordinary pebbles were cold．
So the man sold his few belongings，bought some simple supplies，camped on the seashore，and began testing pebbles．He knew that if he picked up ordinary pebbles and threw them down again because they were cold，he might pick up the same pebble hundreds of times．So，when he felt one that was cold，he threw it into the sea．He spent a whole day doing this but none of them was the touchstone．Yet he went on and on this way．Pick up a pebble．Cold-throw it into the sea．Pick up another．Throw it into the sea．The days continued over a long period of time．
One day，however，about mid-afternoon，he picked up a pebble and it was warm．He threw it into the sea before he realized what he had done．He had formed such a strong habit of throwing each pebble into the sea that when the one he wanted came along，he still threw it away．
So it is with opportunity （機會）．Unless we are cautious （小心的，謹(jǐn)慎的），it's easy to fail to recognize an opportunity when it is in hand and it's just as easy to throw it away．
34．The poor man bought the book becauseA．
A．it was very cheap
B．it was of great value
C．there was a secret in the book
D．he wanted to find the touchstone
35．According to the story，the touchstoneC．
A．is a big pebble
B．feels cold
C．is magic
D．is pure gold
36．The man threw pebbles into the seaC．
A．to test how far he could throw
B．to practice throwing pebbles
C．to avoid picking up the same pebble
D．to express his disappointment
37．What message does the story want to express？D
A．Good habits can lead to success．
B．Habits can only hold you back．
C．Opportunity prefers slow but strong mind．
D．Opportunity only visits the ready and cautious mind．
