Flies that did not avoid the odor when tested individually were less likely than the other flies to avoid the odor when tested in a group.单独测试时没躲开气味的苍蝇在群组测试的时候更不容易躲开。-取反就是 单独测试没躲开的苍蝇在群组测试时候更会躲开，就加强结论，这就证明原来的是削弱结论的。所以不是C
However, when diatoms are observed under constant conditions in a laboratory, they still display periodic behavior, continuing to burrow on schedule for several weeks.
This is not to suggest that the period of this biological clock is immutably fixed.
根据前面不太好判断，因为前面说是几周是不变的。但是后来又说到不是完全fix的。。所以还是选short比较严谨
membership：
[C + sing./pl. v.] （统称）会员，成员；会员人数；成员数
the members, or the number of members, of a group, a club, an organization, etc.
The membership has/have not yet voted.
会员还没有进行投票。
The club has a membership of more than 500.
俱乐部的会员人数超过了500名。
Since 1980, productivity improvements in manufacturing have moved the United States from a position of acute decline in manufacturing to one of world prominence.
错选C：以为是他因。但如果两个的productivity improvements都是因为gains in quality的话，这个他因只能解释both service sector and manufacturing 的productivity 无法提高，但是无法削弱federal budget deficit会产生discrepancy
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考察：
习惯用语：
没有without a nor b的用法
without a or b ✅
without a or without b ✅
neither a nor b ✅
with none+ nor ❌
without a nor b❌
如果前面是否定式动词/介词，而不是neither或者not，则后面用or表示两者否定，不用nor，如：
without A or B=without A or without B, 不能用without A nor without B