闭环控制系统一般有哪几部分组成？ 有哪些作用量和被控制量？

配电装置的汇流母线按（）选择导体。

下列不能用于显示神经内分泌细胞的染色方法是（）

A.碱性重氮反应法

B.DeGrandi改良硝酸银法

C.Lillie-Masson二胺银反应法

D.Gomori-Burtner六胺银反应法

E.Gomori银染色法

投资项目可能有各种各样的风险，如果项目在运营中，由于项目产品销路不畅，产品价格低迷等，致使销售收入达不到预期的目标，则该风险属于( )。

A．市场方面的风险
B．技术方面的风险
C．投资方面的风险
D．配套条件的风险

(B)

Eddie McKay, a once-forgotten pilot, is a subject of great interest to a group of history students in Canada.

It all started when Graham Broad, a professor at the University of Western Ontario, found McKay’s name in a footnote in a book about university history. McKay was included in a list of university alumni (校友) who had served during the First World War, but his name was unfamiliar to Broad, a specialist in military history. Out of curiosity, Broad spent hours at the local archives (档案馆) in a fruitless search for information on McKay. Tired and discouraged, he finally gave up. On his way out, Broad’s glance happened to fall on an exhibiting case showing some old newspapers. His eye was drawn to an old picture of a young man in a rugby uniform.

As he read the words beside the picture, he experienced a thrilling realization. "After looking for him all day, there he was, staring up at me out of the exhibiting case," said Broad. Excited by the find, Broad asked his students to continue his search. They combed old newspapers and other materials for clues. Gradually, a picture came into view.

Captain Alfred Edwin McKay joined the British Royal Flying Corps in 1916. He downed ten enemy planes, outlived his entire squadron(中队) as a WWI flyer, spent some time as a flying instructor in England, then returned to the front, where he was eventually shot down over Belgium and killed in December 1917. But there’s more to his story. "For a brief time in 1916 he was probably the most famous pilot in the world," says Broad. "He was credited with downing Oswald Boelcke, the most famous German pilot at the time." Yet, in a letter home, McKay refused to take credit, saying that Boelcke had actually crashed into another German plane.

McKay’s war records were destroyed during a World War II air bombing on London-an explanation for why he was all but forgotten.

But now, thanks to the efforts of Broad and his students, a marker in McKay’s memory was placed on the university grounds in November 2007. "I found my eyes filling with tears as I read the word ’deceased’ (阵亡) next to his name," said Corey Everrett, a student who found a picture of Mckay in his uniform. "This was such a simple example of the fact that he had been a student just like us, but instead of finishing his time at Western, he chose to fight and die for his country.\

What did the students find out about McKay（）。

A. He trained pilots for some time.

B. He lived longer than other pilots.

C. He died in the Second World War.

D. He was downed by the pilot Boelcke.

令牌总线网在物理上是总线网，而在逻辑上是______网。