A.正确， differences in sth; help的动作发起者是differences所以要用复数
B. Help in doing用法错误
C. Helps应该改成help 因为他的主语是复数的differences
D. Helps应该改成help 因为他的主语是复数的differences
被动表示不简洁;不如A好
2. On Earth, among the surest indications of sunspot cycles are believed to be the rate that trees grow, as seen in the rings visible in the cross sections of their trunks.
(A) On Earth, among the surest indications of sunspot cycles are believed to be the rate that
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treesgrow
(B) On Earth, among the surest indications of sunspot cycles are, it is believed, the rate of tree growth
(C) On Earth, the rate at which trees grow is believed to be among the surest indications of sunspot cycles
(D) Among the surest indications on Earth of sunspot cycles, believed to be the tree growth rate
(E) Among the surest indications on Earth of sunspot cycles is believed to be the rate at which trees grow
此句话地点状语放句首，根据情况是倒装语序，那么应该找到主语，宾语和谓语的关系;根据寻找实义语义的原则，确定本句话的逻辑语义;earth, indications, cycle,rate, growth是本句话的名词，那么就要分析句式确定谁是主语，谁是宾语，谁修饰谁。谓语只有一个is或者are可以确定是be动词。
那么我就来分析此句话earth前面有了一个on, 加了这个on之后就变成状语了，从实际的主语变成了用on引导的状语了，也就是从实义变成了虚义了。所以earth可以确定不是主语。
Cycles和tree growth是用一个of来连接，那么就变成了定语;修饰前面的indications和rate了，句子也就从实义变成了虚义。很显然他们也不是主语或者宾语。
那么第三步我们分析indications和rate, 很快我们发觉indications前面加了among,那么他也不可能是主语，那么我们就知道the rate是主语。Indications是实义宾语;as seen in the rings visible in...引导的同位语，就是修饰主语rate。为了不造成歧义，那么同位语就应该紧跟修饰的主语。 然后我们根据决定这句话的主语和谓语确定他的逻辑语义，还原这句话就变成了：the rate at which tree grow , as seen in the rings visible in the cross sections of their trunks, is believed to be the surest indications of sunspots on earth.
A) among倒装，主语应该是the rate，所以应该用单数is。
(B) among倒装，主语应该是the rate，所以应该用单数is;tree应该用复数，使未划线部分的their有一致的指代对象。
(C) on earth 放置句首修饰整个句子，不符合逻辑;their 的指代存在歧义，离它最近的是 sunspot cycles，未划线部分的 as seen 应该要紧跟其修饰的名词。
(D) tree应该用复数，使未划线部分的their有一致的指代对象;谓语结构不完整，应该用is believed被动语态。
(E) 正确，on Earth修饰indications，主语是the rate，谓语动词用单数is。
3. Although the vast constellation of small islands that dot the South Pacific has a population of only a few million people, it is home to about a sixth of the world's 6,000 or so languages.
(A) Pacific has a population of only a few million people, it is
(B) Pacific has a population of only a few million people, they are
(C) Pacific is populated by a only a few million people, and it is
(D) Pacific, having a population of only a few million people, is nonetheless
(E) Pacific, populated by only a few million people, yet they are
从句主语为单数constellation，主句主语与从句主语保持一致，所以应该使用it指代，谓语be动词 也相应的应该使用is
① 正确
② Although引导的从句主语为单数the constellation，主语的主谓应是it is;不是they are
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③ 连词 and多余 although并列，直接加and 没有主句
④ 句子有although引起的从句，没有主句
⑤ Although引起的从句没有谓语动词;连词yet多余，使句子缺少主句
4. Meteor showers and individual streaks of light that flash across the sky every night are generated when tiny flecks of celestial detritus, often no larger than grains of sand or of pebbles, burn up speeding through the atmosphere.
(A) grains of sand or of pebbles, burn up speeding
(B) grains of sand or pebbles, burn up while speeding
(C) grains of sand or pebbles, which burn up while speeding
(D) a grain of sand or pebble, which burns up as it speeds
(E) a grain of sand or a pebble, burns up when it speeds
1) often no larger than…修饰复数的tiny flecks of celestial detritus，因此，使用复数形式的grains of sand or pebbles比单数的a grain of sand or pebble更为合适，同时，谓语动词相应的也要求是复数的burn up，而不是单数的burns up
2) when引导的状语从句中，tiny flecks of celestial detritus作主语，burn up作谓语，often no larger than…为插入语，不影响句子的基本语法结构
3) grains of sugar/sand/salt等为固定的搭配，类似sugar/sand/salt等细小、沙状的东西才能用 a grain of修饰。Pebbles鹅卵石是大颗的石头，不能用a grain of形容。因此，grains of sand or pebbles这一词组中，pebbles是和grains of平行，而不能与sand平行，作grains of的宾语
A. grains of pebbles是错误的搭配;burn up speeding through…句法错误
B. 正确
C. When引起的状语句子结构不完整，没有谓语
D. When引起的状语句子结构不完整，没有谓语;often no larger than…修饰复数的tiny flecks of celestial detritus，因此，使用复数形式的grains of sand or pebbles比单数的a grain of sand or pebble更为合适
E. often no larger than…修饰复数的tiny flecks of celestial detritus，因此，使用复数形式的grains of sand or pebbles比单数的a grain of sand or pebble更为合适;主语tiny flecks of celestial detritus 要求使用复数谓语burn up
