劳动力在现实中选择跨地区流动时，主要考虑的因素有()。A.地区间人均收入差别大小 B

变压器绕组的额定电压为10KV，则绕组连同套管一起的交流耐压试验电压规定为（）。

A.19KV

B.26KV

C.30KV

室间隔缺损的典型杂音是

A．胸骨左缘第2肋间收缩期杂音Ⅱ级

B．胸骨左缘第2肋间收缩期杂音Ⅲ级

C．胸骨左缘第3～4肋间收缩期杂音Ⅲ级以上

D．胸骨左缘第3～4肋间舒张期杂音Ⅲ级以上

E．胸骨左缘第3～4肋间全收缩期杂音Ⅱ级以上

Until recently, scientists knew little about life in the deep sea, nor had they reason to believe that it was being threatened. Now, with the benefit of technology that allows for deeper exploration, researchers have uncovered a remarkable array of species inhabiting the ocean floor at depths of more than 660 feet, or about 200 meters. At the same time, however, technology has also enabled fishermen to reach far deeper than ever before, into areas where bottom trawls can destroy in minutes what has taken nature hundreds and in some cases thousands of years to build. Many of the world’s coral species, for example, are found at depths of more than 200 meters. It is also estimated that roughly half of the world’s highest seamounts—areas that rise from the ocean floor and are particularly rich in marine life—are also found in the deep ocean. These deep sea ecosystems provide shelter, spawning and breeding areas for fish and other creatures, as well as protection from p currents and predators. Moreover, they are believed to harbor some of the most extensive reservoirs of life on earth, with estimates ranging from 500,000 to 100 million species inhabiting these largely unexplored and highly fragile ecosystems.Yet just as we are beginning to recognize the tremendous diversity of life in these areas, along with the potential benefits newly found species may hold for human society in the form of potential food products and new medicines, they are at risk of being lost forever. With enhanced ability both to identify where these species-rich areas are located and to trawl in deeper water than before, commercial fishing vessels are now beginning to reach down with nets the size of football fields, catching everything in their path while simultaneously crashing fragile corals and breaking up the delicate structure of reefs and seamounts that provide critical habitat to the countless species of fish and other marine life that inhabit the deep ocean floor.Because deep sea bottom trawling is a recent phenomenon, the damage that has been done is still limited. If steps are taken quickly to prevent this kind of destructive activity from occurring on the high seas, the benefits both to the marine environment and to future generations are incalculable. And they far outweigh the short-term costs to the fishing industry.

下列哪种原始血细胞核染色质呈纤细、疏松、网状

A．原单核细胞

B．原红细胞

C．原粒细胞

D．原淋巴细胞

E．原巨核细胞

指示元素概念