法律责任

下述哪项符合溃疡性结肠炎的典型临床表现（）。

A.发热、便秘3个月，伴下腹痛、大便表面带血

B.间断右下腹痛4年，加重伴发热2个月

C.腹泻、左下腹痛6天，伴里急后重，口服利复星后有所好转

D.间断腹泻3年，加重并便鲜血1个月，里急后重，应用利复星后无效

E.间断大便次数增多10年，精神紧张后加重，无便血，便前腹痛，便后缓解，服得舒特后缓解

下图中甲、乙、丙三条曲线分别表示食物中三种营养成分在消化道中的变化情况，下列叙述正确的是

A．甲代表蛋白质

B．乙代表脂肪

C．丙代表淀粉

D．乙能在胃中消化

脑膜刺激征常见于（）。

A.蛛网膜下腔出血

B.脑炎

C.帕金森病

D.脑膜炎

E.椎-基底动脉供血不足

城镇水厂的自用水量应根据原水水质和所采用的处理方法以及构筑物类型等因素通过计算确定，一般可采用设计水量的( )。

A．1%～5%
B．3%～8%
C．5%～10%
D．8%～15%

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.

According to the text, in mate selection human beings（）

A. need symmetry detection

B. need complex three-dimensional images

C. begin to realize their dependence on symmetry

D. cannot be proved whether to rely on asymmetry