Global warming is an issue that worries many people around the world. We already know we can help solve the problem by saving energy and    21       resources.    22    , we may not be aware that changing our diet can help as well.           23      , we can just choose to eat more vegetables and less meat. According to a U.S. study of consumer behavior, meat consumption causes damage    24        the environment. This is because farm animals, such as cows and pigs,    25       methane from their bodies. Many environmental experts believe that methane should be responsible    26        global warming.           27    , the amount of water and land used to produce meat is many times as    28        as that used to grow crops. This shows that vegetarian diet, to some degree, benefits the environment.        In addition, food that travels a long distance to the market is not environmentally friendly, either. Therefore, some people are now    29      the idea of eating local food. Besides counting the calories that our food    30    , we had better remember that long-distance transportation means more consumption of oil.        By eating less meat and choosing locally grown food, we can help save the earth.
【題組】21.
(A) reducing
(B) recycling
(C) refusing
(D) reacting