问题 不定项选择题

下面对某些实验现象的描述,正确的是 [ ]

A.木炭在氧气中燃烧,发出白光

B.氢气在空气中燃烧,产生红色火焰

C.醋酸溶液滴入紫色石蕊试剂,溶液变成蓝色

D.氢氧化钠溶液滴入硫酸铜溶液,出现蓝色沉淀

答案

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单项选择题
单项选择题

Now which are the animals really to be pitied in captivity First, those clever beings whose lively urge for activity can find no outlet behind the bars of the cage. This is most conspicuous, even for the uninitiated, in the case of animals which, when living in a free state, are accustomed to roaming about widely. Owing to this frustrated desire, foxes and wolves housed, in many old-fashioned zoos, in cages which are far too small, are among the most pitiable of all caged animals.
Though pinioned swans generally seem happy, under proper care, by hatching and rearing their young without any trouble, at migration time things become different: they repeatedly swim to the lee side of the pond, in order to have the whole extent of its surface at their disposal, trying to take off. Again and again the grand preparations end in a pathetic flutter of their half wings ; a truly sorry picture !
This, however, rarely awakens the pity of the zoo visitor, least of all when such an originally highly intelligent and mentally alert animal has deteriorated, in confinement, into a crazy idiot, a very caricature of its former self. Sentimental old ladies, the fanatical sponsors of the societies for Prevention of Cruelty to Animals, have no compunction in keeping a grey parrot in a relatively small cage or even chained to a perch. Together with the large corvines, the parrots are probably the only birds which suffer from that state of mind, common to prisoners, namely, boredom.

What effect does confinement have on clever animals, according to the text

A.They never stop trying to escape.

B.They lose all their muscles.

C.They become unhygienic.

D.They may go ma