It is easier to go down the hill than to climb up the hill,so it is easier to fall into bad habits than into good ones.Bad habits do not come suddenly. They come little by little without one being aware of their danger. School boys first pick up little bad habits in the school and on the street. When they can't write their lessons,they copy from their schoolmates. If they see bigger boys smoking,they also want to learn to smoke. If they see their friends gambling ,they want to gamble. When they get bigger,the habits become stronger and stronger,so that they can no longer get rid of(,)them. From copying,they learn to steal,from gambling,they learn to cheat. At last they become distrusted  by everybody. How necessary it is that we get rid of the bad habits in the beginning. When school boys get bigger,their bad habits become   _   .
stronger and stronger weaker and weaker better and better less and less