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Until recently, zoologists believed that all species of phocids (true seals), a pinniped family, use a different maternal Line strategy than do otariids (fur seals and (5) sea lions), another pinniped family. Mother otariids use a foraging strategy. They acquire moderate energy stores in the form of blubber before arriving at breeding sites and then fast for 5 to 11 days after (10) birth. Throughout the rest of the lactation (milk production) period, which lasts from 4 months to 3 years depending on the species, mother otariids alternately forage at sea, where they replenish their fat (15) stores, and nurse their young at breeding sites. Zoologists had assumed that females of all phocid species, by contrast, use a fasting strategy in which mother phocids, having accumulated large energy (20) stores before they arrive at breeding sites, fast throughout the entire lactation period, which lasts from 4 to 50 days depending on the species. However, recent studies on harbor seals, a phocid species, found that (25) lactating females commenced foraging approximately 6 days after giving birth and on average made 7 foraging trips during 29 the remainder of their 24-day lactation period. (30) The maternal strategy evolved by harbor seals may have to do with their small size and the large proportion of their fat stores depleted in lactation. Harbor seals are small compared with other phocid (35) species such as grey seals, northern elephant seals, and hooded seals, all of which are known to fast for the entire lactation period. Studies show that mother seals of these species use respectively 84 percent, (40) 58 percent, and 33 percent of their fat stores during lactation. By comparison, harbor seals use 80 percent of their fat stores in just the first 19 days of lactation, even though they occasionally feed during (45) this period. Since such a large proportion of their fat stores is exhausted despite feeding, mother harbor seals clearly cannot support all of lactation using only energy stored before giving birth. Though smaller (50) than many other phocids, harbor seals are similar in size to most otariids. In addition, there is already some evidence suggesting that the ringed seal, a phocid species that is similar in size to the harbor seal, may also use a maternal foraging strategy.
天山7-Q35: According to the passage, until recently zoologists believed which of the following about all phocid mothers? A. Their fasting periods after giving birth were typically shorter than those of otariids. B. Their lactation periods were generally as long as those of comparably sized otariids. C. They acquired only moderate energy stores in the form of blubber before arriving at breeding sites. D. They depleted less than a third of their stored body fat during lactation. E. The replenished their fat stores only after their lactation period ended.
答案是E，我觉答案应该是A，因为A至少还提到“Zoologists had assumed that females of all phocid species, by contrast, use a fasting strategy in which mother phocids“ 而E中的only太绝对了吧！ | 
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发表于 2007-5-27 23:23:00
