调音台输出电平指示有绿色、黄色和红色三种颜色，黄色区域代表信号电平工作在最佳区域，其

关于脊髓灰质炎减毒活疫苗，正确的说法是

A．冬季肠道疾病较少，对疫苗的干扰作用小，故适于冬季接种

B．疫苗株不耐热，储存和运输中必须冷藏，口服接种应以凉开水送服

C．接种疫苗后通过自然途径感染机体，因此可产生局部分泌型IgA和血清IgG抗体

D．疫苗株有回复突变为野毒株的可能

E．脊髓灰质炎病毒分3个血清型，接种1型疫苗可预防所有3个血清型脊髓灰质炎

凯恩斯主义的实质是

A．自由放任，自由竞争

B．国家对经济生活进行干预调节

C．改变资本主义社会的基本矛盾

D．是西方资本主义国家经济政策的主要依据

二氧化碳、________、________和________等都属于温室气体，造成____到地球上的热量无法向____扩散。

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Watch a baby between six and nine months old, and you will observe the basic concepts of geometry being learned. Once the baby has mastered the idea that space is three-dimensional, it reached out and begins grasping various kinds of objects. It is then, from perhaps nine to fifteen months, that the concepts of sets and numbers are formed. So far, so good. But now an ominous development takes place. The nerve fibers in the brain insulate themselves in such a way that the baby begins to hear sounds very precisely. Soon it picks up language, and it is then brought into direct communication with adults. From this point on, it is usually downhill all the way for mathematics, because the child now becomes exposed to all the nonsense words and beliefs of the community into which it has been so unfortunate as to have been born. Nature having done very well by the child to this point, having permitted it the luxury of thinking for itself for eighteen months, now abandons it to the arbitrary conventions and beliefs of society. But at least the child knows something of geometry and numbers, and it will always retain some memory of the early happy days, no matter what vicissitudes it may suffer later on. The main reservoir of mathematical talent in any society is thus possessed by children who are about two years old, children who have just learned to speak fluently.

Which of the following activities would teach a baby about geometry().

A. Picking up language.

B. Communicating with others.

C. Recognizing numbers.

D. Catching different objects.