惩罚也是一种教育手段。

电子商务中的瓶颈是______。

A．信息技术

B．管理方法

C．配送体系

D．商务标准

“C to C”模式是指“ （ ） ”模式。

A．企业－企业

B．企业－政府

C．企业－消费者

D．消费者－消费者

下列不属于足太阳膀胱经的头穴线是（）

A.额旁1线

B.顶旁1线

C.顶旁2线

D.枕上旁线

E.枕下旁线

中型火力发电厂的装机容量为( )。

A．大于25万kW

B．2.5万～25万kW

C．小于2.5万kW

D．110万～500万kW

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.

According to the passage, what is ATP

A．A biochemical process.

B．The tip of a root.

C．A chemical compound.

D．A type of plant cell.