更多"It's generally agreed that fluctuat"的相关试题:
[单项选择]Baby boom' refers to the great increase of birth rate between ______.
A. 1946 and 1964
B. 1860 and 1890
C. 1920 and 1935
D. 1845 and 1854
[单项选择]All the members of the committee agreed that Mr. Smith was the right person to hold such an important position. They made an ______ decision.
A. simultaneous
B. subsequent
C. unanimous
D. arbitrary
[单项选择]Afghanistan's Taliban factions have agreed to free Iranian prisoners in exchange for ______.
A. Taliban capital held by Iran and the Afghan opposition
B. Taliban members held by Iran and the Afghan opposition
C. Taliban cities held by Iran and the Afghan opposition
D. Taliban territories held by Iran and the Afghan opposition
[单项选择]Soap operas have helped in lowering Brazil's birth rate because ______.
[单项选择]
It’s generally agreed that the greatest threat facing the world today is the warming of the earth’s atmosphere, commonly called global warming or the greenhouse effect. But what is the cause of the greenhouse effect
We have been producing too many of the gases which, when they are released into the earth’s atmosphere, trap heat, and thus raise their temperatures. There are several gases involved, but the main ones are carbon dioxide (二氧化碳) and chlorofluorocarbons (氯氟甲烷)--often called CFCs. The carbon dioxide comes from burning forests and from bunting fossil fuels such as oil and coal. The CFCs are given off by refrigerators and air-conditioning systems. Carbon dioxide is to blame for 56% of the greenhouse effect, and CFCs for 23%.
The global warming we are experiencing now is only a result of the carbon dioxide and other gases we have dumped into the atmosphere up to the 1960s. In other words, the damage may have already been done. Tempe
A. 1 to 4 degrees C
B. 3 degrees C
C. over half a degree C
D. 1.3 degrees C
[单项选择]有两个关系R和S，分别包含15个和10个元组，则在R∪S，R—S，R∩S中不可能出现的元组数目情况是________。
A. 15,5,10
B. 18,17,7
C. 21，11,4
D. 25,15,0
[单项选择]设R和S分别是r和s元关系，且R有n个元组，S有m个元组。执行关系R和S的笛卡儿积，记为T=R×S，则（）
A. T的元数是(r+s)，且有(n+m)个元组
B. T的元数是(r+s)，且有(n×m)个元组
C. T的元数是(r×s)，且有(n+m)个元组
D. T的元数是(r×s)，且有(n×m)个元组
[单项选择]若关系R和S模式相同，R有6个元组，S有8个元组，则下列表示R∪S、R∩S结果关系元组数的4种情况中，不可能出现的是( )。
A. 8，6
B. 10，1
C. 11，3
D. 14，0
[单项选择]设关系R和S的元数分别是r和s，且R有n个元组，S有m个元组。执行关系R和S的笛卡儿积，记为T=R×S，则（）。
A. T的元数是r+s，且有n+m个元组
B. T的元数是r+s，且有n×m个元组
C. T的元数是r×s，且有n+m个元组
D. T的元数是r×s，且有n×m个元组
