读可持续发展复合系统示意图（下图），图中①、②、③、④号码的含义分别是（）A、①经济

下面关于计算机病毒的叙述中，不正确的是_______。

A．计算机病毒有破坏性，凡是软件作用到的计算机资源，都可能受到病毒的破坏

B．计算机病毒有潜伏性，它可能长期潜伏在合法的程序中，遇到一定条件才开始进行破坏活动

C．计算机病毒有传染性，它能不断扩散，这是计算机病毒最可怕的特性

D．计算机病毒是开发程序时未经测试而附带的一种寄生，它能在计算机系统中存在和传播

下列有关油脂的叙述不正确的是（　　）

A．油脂有油和脂肪之分，但都是高级脂肪酸与甘油形成的酯

B．糖类、油脂、蛋白质均是由C、H、O三种元素组成的高分子化合物

C．油脂没有固定的熔沸点

D．植物油能使溴水、酸性高锰酸钾溶液褪色，也能与H₂发生加成反应

分部分项工程完成后，应在施工单位自行验收合格后，再通知工程监理验收，重要的分部分项工程应请（）参加验收。

A．施工单位

B．设计单位

C．建设单位

D．监理单位

动脉粥样硬化预后与哪些无关（）

A.有无并发症

B.受累器官受损情况

C.病变部位

D.发病时间

E.血管狭窄发展速度

Since the 1930s, the idea that creatures might advertise their " fitness " as mates through symmetry has been around. It rests on the notion that factors ranging from bad genes to coming off worse in too many fights will lead to asymmetries others can see. And over the past few years, experiments with animals and humans seemed to support the idea that symmetry in features such as plumage and facial characteristics influences mate selection.

But no one had actually checked that the animals in these experiments can actually see the subtle differences in symmetry, typically of between 1 and 2 percent. Now the first such experiment has been carried out. The results are worrying for advocates of symmetry detection as a powerful factor in mate selection.

John Swaddle, an ethnologist at the University of Bristol, performed the experiment using wild starlings, which have excellent eyesight. He trained them to hit keys marked with bar patterns with varying levels of asymmetry in order to receive food rewards. This showed the starlings could easily detect asymmetries of between 5 and 10 percent. But at between 1 and 2 percent, their performance plummeted to no better than random guessing.

" This suggests that the levels of asymmetry that birds encounter in nature will often be just too small to be detected, " says Swaddle. He says experiments that linked small asymmetries to fitness may have produced misleading correlations, and says the only direct evidence that birds use asymmetry as a cue to mate fitness involves levels of asymmetry of at least 10 percent. " I think signaling by asymmetry will probably only occur when species show such very large asymmetries—and this doesn’t occur that often. "

This raises questions about research suggesting that humans are influenced by visual asymmetry in their choice of partner. Michael Butt of the Perception Laboratory at the University of St. Andrews, who has carried out such experiments, concedes that no one has ever checked if humans have a threshold to asymmetry detection. He thinks a conclusive test of this would probably involve manipulating complex three-dimensional images: " It would be a very difficult experiment to do "

Burt adds that the abilities of animals to detect asymmetry in bar patterns may not reflect their talent for spotting asymmetries in body shape. " The visibility of an asymmetry may well depend on its type, " he says. Swaddle agrees, and is planning further experiments. " But I suspect that asymmetry is used as a visual cue less often than most people appear to presume, " he warns.

John Swaddle’s experiment suggests that（）

A. asymmetry is seldom big enough

B. fitness may cause incorrect relations

C. birds occasionally rely on symmetry in mate selection

D. random guessing is sometimes as good as asymmetry detection