1,Parland’s alligator population has been declining in recent years，primarily because of hunting. Alligators prey heavily on a species of freshwater fish that is highly valued as food by Parilanders，who had hoped that the decline in the alligator population would lead to an increase in the numbers of these fish available for human consumption. Yet the population of this fish has also declined，even though the annual number caught for human consumption has not increased.
P地区的短吻鳄数量近些年下降，主要原因是捕猎。短吻鳄捕食的淡水鱼是P居民的食物，P居民希望短吻鳄数量的下降可以导致这种可供人们消费的鱼的数量上升。但是这种鱼的数量也下降了，尽管它每年被人类抓住消费的的量没有增加。
Which of following，if true，most help to explain the decline in the population of the fish species?
下列哪个选项如果是对的，最有效地解释了鱼的数量下降?
A.The decline in the alligator population has meant that fishers can work in some parts of lakes and rivers that were formerly too dangerous.
短吻鳄数量的下降意味着渔民可以到以前湖里和江河里那些以前很危险的地方工作。
B.Over the last few years，Parland’s commercial fishing enterprises have increased the number of fishing boats they use.
过去几年，P的渔业公司增加了它们使用的捕鱼船数量。
C.The main predator of these fish is another species of fish on which alligator also prey.
这种鱼的主要捕食者是另一种也被短吻鳄捕食的鱼
D.Many Parlanders who hunt alligators do so because of the high market price of alligator skins，not because of the threat alligators pose to the fish population.
许多居民捕猎短吻鳄是因为鳄鱼皮市场价格高，而不是因为它威胁到鱼的数量。
E.In several neighboring countries through which Parland’s rivers also flow，alligators are at risk of extinction as a result of extensive hunting.
在一些P河流经的邻近国家，短吻鳄有灭绝的危险因为捕猎。
解析：
A.渔民在哪工作，不能解释为什么短吻鳄数量下降，淡水鱼的数量也下降。
B.易错项。文章说得很清楚，人们消费捕食鱼的数量没有上升，所以即使增加了捕鱼船的数量，也不能说明鱼被捕的多，所以不能解释鱼的数量下降。
C.正确答案。由于短吻鳄的数量减少，另一种该淡水鱼的捕食者数量就很可能增加，是它们捕食更多的淡水鱼，解释了为什么淡水鱼的数量减少。
D.捕猎短吻鳄的原因，和文章要解释现象，即为什么鱼的数量下降无关。
E.短吻鳄有灭绝风险，和文章要解释现象，即为什么鱼的数量下降无关。
思路：文章中出现上升下降，正确答案往往体现出变化。
变化：短吻鳄变少
相应变化：鱼的另一种捕食者数量变多
