Grassland songbirds often nest in the same grassland-wetland complexes aswaterfowl, particularly in a certain part of those complexes, namely, uplandhabitats surrounding wetlands. Although some wildlife management proceduresdirected at waterfowl, such as habitat enhancement or restoration, may alsobenefit songbirds, the impact of others, especially the control of waterfowlpredators, remains difficult to predict. For example, most predators of waterfowlnests prey opportunistically on songbird nests, and removing these predatorscould directly increase songbird nesting success. Alternatively, small mammalssuch as mice and ground squirrels are important in the diet of manywaterfowl-nest predators and can themselves be important predators of songbirdnets. Thus. Removing waterfowl-nest predators could affect songbird nestingsuccess through subsequent increases in small-mammal populations.

    In 1995 and 1996,researchers trapped and removed certain waterfowl-nest predators, primaryraccoons and striped skunks, then observed subsequent survival rates forsongbird nests. Surprisingly. They observed no significant effect on songbirdnesting success. This may be due to several factors. Neither raccoons nor striped skunks consume groundsquirrels, which are important predators of songbird nests. Thus, theirremoval may not have led to significant increases in populations of smallerpredators. Additionally, both raccoons and striped skunks prefer wetlands andspend little time in upland habitats; removing these species may not haveincreased the nesting success of songbirds in the uplands enough to allowdetection.

According to the passage, which of the following is true about the role played by ground squirrels in the ecology of grassland-wetland complexes?

A.     While not important in the diet of raccoons or striped skunks, ground squirrels are a significant source of food for other waterfowl-nest predators.

B.      Whereas ground squirrels are typically important as predators of songbird nests, their opportunistic predation on waterfowl nests also has an observable effect on waterfowl nesting success.

C.     Although most waterfowl-nest predators prey on small mammals such as mice and ground squirrels, populations of ground squirrels tend to increase quickly enough to compensate for thislevel of predation.

D.     Although ground squirrels have been known to prey on songbird nests, a larger portion of theirdiets is usually provided by predation onwaterfowl nests.

E.      Since larger predators tend to prefer small mammals to songbird eggs as a food source, alarge population of ground squirrels plays an important role in controllingopportunistic predation on songbirdnests.

OA is A.  但是我认为A是不正确的, "ground squirrels are a significant source of food for other waterfowl-nest predators." 原文中明确提到的是"ground squirrels are important in the diet of manywaterfowl-nest predators, Neither raccoons nor striped skunks consume groundsquirrels". 即除了R&S, 松鼠是许多W-N predators的食物, 而A的意思是说"除了R&S, 松鼠是其它W-N predators的食物." 明显扩大了把松鼠当作食物的W-N predators的范围. 如果A中的other改成"many other"的话, 则A才是一个可以接受的答案.