Bears and humans often meet in National Parks． 1 campers and hikers are warned not to feed the bears-many people ignore these warnings and feed the bears 2 ．When bears are used to people’s food- 3 soon arise．Bears like to eat a large variety of things-both meat and vegetables．Without human assistance-bears live 4 on roots-twigs-leaves of trees-insects and small animals．With people 5 -the bears’ tastes quickly 6 to include sandwiches-hot dogs-hamburgers-and anything else they can temp humans into 7 ．
Bears often 8 clever strategies(策略) for getting people to let go their food supplies． 9 -an unsuspecting(无戒备心的) hiker has taken off his or her pack for a rest only 10 a bear charge out of the woods- 11 the pack and quickly disappear into the underbrush with it．Hanging the pack on the tree branch won’t 12 ．
Bears have been known to climb up-jump off-and catch the pack on the 13 down．One mother bear stretched up with her baby on her shoulders to reach a pack stored on a pole．Many bears 14 people into giving up their supplies．Although a bear is 15 to attack a person and would probably run away 16 screamed at-few people are willing to do so．Most people 17 the pack and run the other way．This-of course-delights the bear．In some places-the Park Service installed(安装；设置) some metal barrels with lids to help campers keep their 18 safe from bears．Although the bears were unable to open these containers-the effort was 19 successful．Most campers-unable to 20 the metal drums from rubbish cans-never used them for the intended purpose．