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A．It can cause flooding in an
B．It can carry diseases that affect animals.
C．It can introduce too much salt into the soil.
D．It can divert water from important crops.

A.It
B.It
C.
C．It
D.
D．It

【参考答案】

C
解析：According?to?the?speaker,?what?is?the?main?problem?......

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听力原文： I've mentioned how DNA have solved many mysteries in biology. And today I want to talk about how it might relate to hypothesis about the travels of the green turtle. Every winter some green turtles make a 2000 km journey from Brazil to Ascension Island in the middle of Atlantic, where they mate and lay eggs. But the question is why do they travel so far to lay their eggs? One researcher hypothesized that there are two parts to the explanation. One is natal homing, the instinct that drives green turtles to always return to the beach where they were hatched. The second part has to do with continental drift, the theory that the positions of earth continents have changed considerably overtime. Brazil and Ascension Island were once much closer together, and continental drift drove them apart. But the turtles kept on going back to the island where they hatched. However another scientist question this explanation on the ground that it would be very unlikely that conditions would allowe generations of turtles over hundreds of millions of years to keep going back to the same nesting ground every single year. So, what is the connection to DNA? Well, there are groups of green turtles that nest in locations other than the Ascension Island. If green turtles always return to the place where they were hatched, then the turtles that have been going to the Ascension Island to nest would've been genetically isolated long enough to have DNA that was very different from the green turtles that nest else where. But when scientists examine DNA from these turtles, their DNA wasn't that different from the DNA of the turtles that go to Ascension Island. Do you have a shock? Well, we still don't know the answer to the question about why a certain group of turtles go to Ascension Island, but this study was a nice example of the usefulness of DNA analysis to biology.(44)A．A possible explanation for why green turtles nest in certain locations.B．Physical differences among various groups of green turtles.C．Several examples of mating behavior. in green turtles.D．The impact of continental drift on the diet of green turtles.

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阅读以下说明和C语言函数，将应填入(n)处的字句写在对应栏内。【说明】函数count months(DATE start，DATE end)的功能是：计算两个给定日期之间所包含的完整月份数。该函数先算出起止日期中所含的完整年数，再计算余下的完整月份数。规定两个相邻年份的同月同日之间的间隔为1年。例如，2007.5.30—2008.5.30的间隔为1年。若相邻两年中前一年是闰年，并且日期是2月29日，则到下一年的2月28日为1年，即2008.2.29—2009.2.28的间隔为1年。规定两个相邻月份的相同日之间的间隔为1个月，但需要特别考虑月末的特殊情况。例如，2007.1.29—2007.2.28的间隔为1个月，同理，2007.1.30—2007.2.28、2007.1.31—2007.2.28的间隔都是1个月。计算起止日期间隔不足一年的完整月份数时，分如下两种情况。 (1)起止日期不跨年度。先用终止日期的月号减去起始日期的月号得到月份数，然后再根据情况进行修正。例如，起止日期为2008.3.31—2008.9.20，通过月号算出月份数为6。修正时，通过调用函数makevalid将2008.9.31改为2008.9.30，与终止日期2008.9.20比较后，将月份数修正为5。 (2)起止日期跨年度。计算方法如下例所示：对于起止日期2008.7.25—2009.3.31，先计算2008.7.25—2008.12.25的月份数为5，再算出2008.12.25—2009.3.25的月份数为 3，因此2008.7.25—2009.3.31之间的完整月份数为8。日期数据类型定义如下： typedef struct{ int year; int month; int day; *日期的年号(4位)、月和口号* }DATE; 程序中使用的函数cmp_date()、isLeap Year()和makevalid()说明如下。[*]【C语言函数】 int count_months (DATE start，DATE end) { int years = 0, months = 0; DATE r; if (cmp_date(start,end) ＞ 0) { r = start; start = end; end = r; } years = end.year - start.year; *计算年数* r = start; r.year = end.year; if (cmp_date(r, end) ＞ 0) { *修正年数* (1); r.year--; } if (r.year ＜ end.year) { *跨年度时，先计算到12月的月份数* months =(2); r.month = 12; } months += (end.month + 12 - r.month) % 12; r.year = end.year; r.month = end.month; makevalid ((3)); *将日期r修正为有效日期* if (cmp_date(r,end) ＞ 0) *修正月份数* (4); months +=(5); *计算总月份数* return months; }使用的函数cmp_date()、isLeap Year()和makevalid()说明如下。[*]

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