短期国债的常见形式是国库券。（）

下图是信风带某海区表层水温空间分布示意图，完成题。

小题1:图示水温分布情况最有可能出现在

A．南半球

B．北半球

C．大陆东岸

D．大陆西岸小题2:图示洋流可能是

A．墨西哥湾暖流

B．日本暖流

C．东澳大利亚暖流

D．巴西暖流

下列句子没有语病的一项是：[ ]

A、回想自己走过的道路，我深深地体会到人生的价值在于奉献。

B、我们肩负着建设祖国和保卫祖国。

C、我用了整整一小时左右，才写完了这篇作文。

D、语言通顺，这是衡量一篇作文好坏的重要标准之一。

如图所示，匀强磁场的磁感应强度为B，方向竖直向下，在磁场中有一个边长为L的正方形刚性金属框abcd，框ab边的质量为m，电阻为R，其他三边的质量和电阻均不计。cd边上装有固定的水平轴，金属框可绕cd轴自由转动。将金属框自水平位置由静止释放，重力加速度为g，在金属框第一次转到竖直位置的过程中，下列说法正确的是

A．通过ab边的电流方向为b→a

B．ab边经过最低点时的电动势为BL

C．a、b两点间的电压逐渐变大

D．整个过程中，通过电阻R的电荷量为，与转动的快慢无关

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 word "themselves" in Paragraph 1 refers to________.

A．plant physiologists

B．solutions

C．laboratory flasks

D．roots

电气设备检修中更换的零部件，技术性能（）原设计的要求。