下述激素必须通过细胞膜上受体才能发生效应的有（） A.血管升压素、胰岛素样生长因子和

凝血过程中必不可少的离子是（）

A.钙离子

B.镁离子

C.钾离子

D.氯离子

E.钠离子

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 free 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 withorganic 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.

Roots have the ability to ______.

A．make proteins

B．obtain fresh air

C．produce inorganic nitrogen

D．carry out activities without energy

在CVOR辐射场中（）。

A.基准相位信号是30Hz对载波调幅后直接得到的

B.基准相位信号是30Hz对载波调频后直接得到的

C.基准相位信号是30Hz对副载波调频、再对载波调幅后得到的

纪律处分条例规定从重或者加重处分的情形有（）。

A.在纪律集中整饬过程中，不收敛、不收手的

B.强迫、唆使他人违纪的

C.本条例另有规定的

D.不如实提供证据、串供的

新型发动机有几个慢车转速？如何转换？