When young, Jack was very     1    , who worked     2    hard on scientific research. He     3     his career and barely     4     his attention to other things. After a couple of     5    , he made a big     6     and won a good fame in the     7    field. However,     8     most successful people, he is leading a simple life.     9    , he still lives in a small room with little     10    now. Last week, he signed a     11     with a charity concerned about    12    . He gave away all his money to the charity to     13     in environmental protection. It is his     14     to our environment that     15     other ordinary people.