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听力原文:W: Today we have with us Dr Michael White, a space scientist, to tell us about a new space plane that British scientists are working on. Firstly, Dr White, could you tell us what the space plane looks like? M: Well, it looks just like an ordinary plane, really. It’s about the same size as a plane, and it can carry about 50 passengers. W: But it doesn’t act like an ordinary plane, does it? M: No, it’s much faster. For example, you could fly from London to Beijing in only 30 minutes. W: My goodness! And how does it work? M: Well, shortly after taking off, the plane leaves the earth’s atmosphere and goes into orbit around the earth until it returns to the ground. W: So it’s really a kind of space rocket. M: Not really, no, for two reasons. First, a space rocket can only be used once, but this space plane can be used for many times. Second, while the plane is traveling through the atmosphere, the pilot can fly it just like an ordinary plane. W: It sounds very exciting. (20)
A.
A satellite.
B.
An ordinary plane.
C.
A space plane.
D.
A space rocket.
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【单选题】已知有向图G=(V,E),其中V={V 1 ,V 2 ,V 3 ,V 4 ,V 5 ,V 6 ,V 7 },庐{ 1,V 2 >, 1,V 3 >, 1,V 4 >, 2,V 5 >, 3,V 5 >, 3,V 6 >, 4,V 6 >, 5,V 7 >, 6,V 7 >},G的拓扑序列是( )。【北京航空航天大学2000一、7(2分)】
A.
V\r\n 1 \r\n,V\r\n 3 \r\n,V\r\n 4 \r\n,V\r\n 6 \r\n,V\r\n 2 \r\n,V\r\n 5 \r\n,V\r\n 7
B.
V\r\n 1 \r\n,V\r\n 3 \r\n,V\r\n 3 \r\n,V\r\n 6 \r\n,V\r\n 4 \r\n,V\r\n 5 \r\n,V\r\n 7
C.
V\r\n 1 \r\n,V\r\n 3 \r\n,V\r\n 4 \r\n,V\r\n 5 \r\n,V\r\n 2 \r\n,V\r\n 6 \r\n,V\r\n 7
D.
V\r\n 1 \r\n,V\r\n 2 \r\n,V\r\n 5 \r\n,V\r\n 3 \r\n,V\r\n 4 \r\n,V\r\n 6 \r\n,V\r\n 7
【简答题】按传输媒介分类,根据信号传输媒介的不同可将通信系统分为 通信系统和 通信系统 两大类。
【多选题】按传输媒介,通信系统可分为( )。
A.
有线通信
B.
无线通信
C.
数字通信
D.
模拟通信
【简答题】通信系统 按传输媒介 可分为 通信系统和 通信系统。
【多选题】按传输媒介,通信系统可分为
A.
模拟系统
B.
数字系统
C.
有线系统
D.
无线系统
【简答题】按传输媒介,通信系统可分为 通信系统 通信系统。
【单选题】劳尔氏菌属(Ralstonia)是由原( )中独立出来的。
A.
假单胞菌属
B.
黄单胞菌属
C.
欧文氏菌属
D.
土壤杆菌属
【单选题】向量组α 1 =(1,3,5,-1) T ,α 2 =(2,-1,-3,4) T ,α 3 =(6,4,4,6) T ,α 4 =(7,7,9,1) T ,α 5 =(3,2,2,3) T 的极大线性无关组是( )
A.
α\r\n 1 \r\n,α\r\n 2 \r\n,α\r\n 5 \r\n。
B.
α\r\n 1 \r\n,α\r\n 3 \r\n,α\r\n 5 \r\n。
C.
α\r\n 2 \r\n,α\r\n 3 \r\n,α\r\n 4 \r\n。
D.
α\r\n 3 \r\n,α\r\n 4 \r\n,α\r\n 5 \r\n。
【简答题】按传输媒介,通信系统可分为 通信系统和 通信系统。
【多选题】按传输媒介,通信系统可分为( )和( )两大类。
A.
有线通信系统
B.
无线通信系统
C.
模拟通信系统
D.
数字通信系统
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