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小华和小红同学为了研究泡沫塑料和棉絮的保温性能，她们取大小厚度相同的泡沫塑料和棉絮，分别包住装有初温相同的等量热水的烧瓶，利用温度计和手表定时测量烧瓶中水的温度，得到如下数据：

t/min0102030455060708090100110120
泡沫塑料T1/℃80706255493740373534343333
棉    絮T2/℃80655445404435343433333333
（1）在他们记录的数据中，某一组数据有问题，请你找出错误的一组数据是在______min时测量的．

（2）分析表中数据，可以看出：温度越高冷却得越______（快/慢）．

（3）改正错误数据后分析可以看出______的保温性能更好些，当时的室温是______℃．

（4）在实验中，如果热水的质量不等，______（能/不能）得到以上的实验结论．

答案

从表中数据可知，相同时间段内，用棉絮包的烧瓶水的温度始终比用泡沫塑料包的烧水的温度低，只有在第50min时不一样，说明这组数据错了；

由表中的数据可知，最后水的温度和室温相同，所以室温为33℃，经过110分钟，泡沫塑料包的烧瓶温度从80℃降到33℃，降低了47℃；而棉絮包的烧瓶水从80℃降到33℃，用了90分钟，由此可见，泡沫塑料的保温性能比棉絮好；

本题中采用控制变量法，取大小厚度相同的泡沫塑料和棉絮，分别包住装有初温相同的等量热水的烧瓶，研究温度的变化．

答：（1）50；

（2）快；

（3）泡沫塑料，33℃；

（4）不能．

单项选择题


In this section you will find after each of the passages a number of questions or unfinished statements about the passage, each with 4 (A, B, C and D) choices to complete the statement. You must choose the one which you think fits best. The time for this section is 75 minutes.

questions 1-5 are based on the following passage.
Non-indigenous (non-native) species of plants and animals arrive by way of two general types of pathways. First, species having origins outside the United States may enter the country and become established either as free-living populations or under human cultivation-for example, in agriculture, horticulture, aquaculture, or as pets. Some cultivated species subsequently escape or are released and also become established as free-living populations. Second, species of either US or foreign origin and already within the United States may spread to new locales. Pathways of both types include intentional as well as unintentional species transfers. Rates of species movement driven by human transformations of natural environments as well as by human mobility-through commerce, tourism, and travel-greatly exceed natural rates by comparison. While geographic distributions of species naturally expand or contract over historical time intervals (tens to hundreds of years), species-ranges rarely expand thousands of miles or across physical barriers such as oceans or mountains.
Habitat modification can create conditions favorable to the establishment of non-indigenous species. Soil disturbed in construction and agriculture is open for colonization by non-indigenous weeds, which in turn may provide habitats for the non-indigenous insects that evolved with them. Human-generated changes in fire frequency, grazing intensity, as well as soil stability and nutrient levels similarly facilitate the spread and establishment of non-indigenous plants. When human changes to natural environments span large geographical areas, they effectively create passages for species movement between previously isolated locales. The rapid spread of the Russian wheat aphid to fifteen states in just two years following its 1986 arrival has been attributed in part to the prevalence of alternative host plants that are available when wheat is not. Many of these are non- indigenous grasses recommended for planting on the forty million or more acres enrolled in the US Department of Agriculture Conservation Reserve Program.
A number of factors perplex quantitative evaluation of the relative importance of various entry pathways. Time lags often occur between establishment of non-indigenous species and their detection, and tracing the pathway for a long-established species is difficult. Experts estimate that non-indigenous weeds are usually detected only after having been in the country for thirty years or having spread to at least ten thousand acres. In addition, federal port inspection, although a major source of information on non-indigenous species pathways, especially for agriculture pests, provides data only when such species enter via closely-examined routes. Finally, some comparisons between pathways defy quantitative analysis-for example, which is more "important": the entry path of one very harmful species or one by which many but less harmful species enter the country

According to the passage, the US Department of Agriculture______.

A．is liable for the fast distribution of the Russian wheat pest

B．fails to isolate the Russian wheat aphid in limited locales

C．provides data about foreign species entering the country by regulated routes

D．is responsible for introducing harmful plants onto federal lands
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判断题

直流牵引电机仅采用调压调速。
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