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问题 多项选择题

纳税人办理纳税申报时应当如实填写纳税申报表，并根据不同情况相应报送下列有关证件资料。( )

A．财务会计报表及有关说明材料

B．与纳税有关的合同、协汉书

C．外出经营活动税收管理证明

D．境内或者境外公证机构出具的有关证明文件

答案

参考答案：A,B,C,D

选择题
已知直线x-y-1=0与y=x2+a相切，则a等于（　　）
A．4B．
1
2
C．-
1
4
D．-
3
4
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单项选择题

About fifty years ago, plant physiologists set out to grow roots by themselves in solutions in laboratory flasks. The scientists found that the nutrition of isolated roots was quite simple. They required sugar and the usual minerals and vitamins. However, they did not require organic nitrogen compounds. These roots got along fine on mineral inorganic nitrogen. Roots are capable of making their own proteins and other organic compounds. These activities by roots require energy, of course. The process of respiration uses sugar to make the high energy compound ATP, which drives the biochemical reactions. Respiration also requires oxygen. Highly active roots require a good deal of oxygen.The study of isolated roots has provided an understanding of the relationship between shoots and roots in intact plants. The leaves of the shoots provide the roots with sugar and vitamins, and the roots provide the shoots with water and minerals. In addition, roots can provide the shoots with organic nitrogen compounds. This comes in handy for the growth of buds in the early spring when leaves are not yet functioning. Once leaves begin photosynthesizing, they produce protein, but only mature leaves can "export" protein to the rest of the plant in the form of amino acids.

What is the main topic of the passage

A．The relationship between a plant’s roots and its shoots.

B．What can be learned by growing roots in isolation.

C．How plants can be grown without roots.

D．What elements are necessary for the growth of plants.
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