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问题 单项选择题

股票加看跌期权组合，称为( )。

A．抛补看涨期权
B．保护性看跌期权
C．多头对敲
D．空头对敲

答案

参考答案：B

解析： 股票加看跌期权组合，称为保护性看跌期权。因为单独投资于股票风险很大，如果同时增加看跌期权，可以降低投资的风险。

单项选择题

急性胰腺炎休克的主要原因是（）

A.神经源性

B.用哌替啶

C.心肌损害

D.感染

E.有效血容量不足
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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.

The use of the phrase "comes in handy" in Paragraph 2 indicates that the process is________.

A．unavoidable

B．predictable

C．necessary

D．successful
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