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。
as much as 20 percent为插入语不再修饰hours => 想问一下为什么不可以修饰hours