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酸碱指示剂的选择原则是指示剂的变色范围应恰在滴定的突跃范围内,或至少占突跃范围的一部分。

A. 对
B. 错

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药物的鉴别方法 蔗糖

A. Keller-Kiliani反应
B. 与碱性酒石酸铜试液产生砖红色沉淀
C. 加硫酸水解后,加碱性酒石酸铜产生砖红色沉淀

I was introduced to the concept of literacy animator in Oladumi Arigbede’s (1994) article on high illiteracy rates among women and school dropout rates among girls. According to Arigbede, literacy animators view their role as assisting in the self-liberating development of people in the world who are struggling for a more meaningful life. Animators are a family of deeply concerned and committed people whose gut-level rejection of mass human pauperizafion compels them to intervene on the side of the marginalized. Their motivation is not derived from a love of literacy as merely another technical life skill, and they accept that literacy is never culturally or ideologically neutral. Arigbede writes from her experiences as an animator working with women and men in Nigeria. She believes that literacy animators have to make a clear choice about whose culture and whose ideology will be fostered among those with whom they work. Do literacy educators in the United States consider whether the instruction they pursue conflicts with their students’ traditional cultures or community, or fosters illiteracies in learners’ first or home languages or dialects and in their orality Some approaches to literacy instruction represent an ideology of individualism, control, and competition. Consider, for example, the difference in values conveyed and represented when students engage in choral reading versus the practice of having one student read out loud to the group. To identify as a literacy animator is to choose the ideology of "sharing, solidarity, love, equity, co-operation with and respect of both nature and other human beings". Literacy pedagogy that matches the animator ideology works on maintaining the languages and cultures of millions of minority children who at present are being forced to accept the language and culture of the dominant group. It might lead to assessment that examines the performance outcomes of a community of literacy learners and the social significance of their uses of literacy, as opposed to measuring what an individual can do as a reader and writer on a standardized test. Shor(1993) describes literacy animators as problem-posing, community-based, dialogic educators. Do our teacher-education textbooks on reading and language arts promote the idea that teachers should explore problems from a community-based dialogic perspective According to the author, "choral reading" may represent ______.

A. individualism
B. collectivism
C. competition
D. immersion

Before set up his pizza delivery service, he

A. tested samples on potential clients.
B. handed out product questionnaires.
C. assessed demand in different areas.
D. trained staff for a few months.

If a mother pushes her small son in a swing, giving only a light force each time he returns, eventually he will be swinging quite high. The child can do this for himself by using his legs to increase the motion, but both the mother’s push and the child’s leg movements must occur at the proper moment, or the extent of the swing will not increase. In physics, increasing the swing is increasing the amplitude; the length of the rope on the swing determines its natural oscillation period. This ability of an object to move periodically or to vibrate when stimulated by a force operating in its natural period is called resonance. Resonance is observed many times without consciously thinking about it; for example, one may find an annoying vibration or shimmy in an automobile, caused by a loose engine mount vibrating with increasing amplitude because of an out-of-round tire. The bulge on the tire slaps the pavement with each revolution; at the natural resonance point of the engine mount, it will begin to vibrate. Such vibrations can result in considerable damage if allowed to persist. Another destructive example of resonance is the shattering of a crystal goblet by the production of a musical tone at the natural resonant point of the goblet. The energy of the sound waves causes vibration in the glass; as its amplitude increases, the motion in the glass exceeds the elasticity of the goblet, and it shatters. An instrument called a tachometer makes use of the principle of resonance. It consists of many tiny bars, loosely fastened together and arranged so that each bar can slide independently of the others. Movement of the bars causes changes in a dial. When placed next to a rotating motor or engine, the tachometer picks up slight vibrations which are transferred to the resonant bars. These bars begin to move, and the resulting dial may be read to find the revolutions per minute of the motor very quickly. A tachometer is an instrument that uses resonance to determine ______.

A. the speed of a motor in revolutions
B. the frequency at which a motor vibrates
C. the amplitude of an engine that oscillates
D. the changes in a dial within a car engine

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