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蝴蝶为昆虫纲鳞翅目锤角亚目动物的统称，全世界有14000多种。蝴蝶幼虫嗜食叶片，成虫大部分吸食花蜜。下列有关叙述错误的是( )。 A.16平方米草地上有8只蝴蝶可以表示蝴蝶的种群密度 B.若调查一长方形地块中某蝴蝶幼虫的种群密度，可用等距取样法取样 C.诱捕某种蝴蝶的雄性个体，会降低该种蝴蝶的种群密度 D.蝴蝶属于初级消费者，能加快生态系统的物质循环
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【简答题】When you go to St．Petersburg, the number of attractions can seem large．If you are short of time, or just want to make sure to hit the highlights , these are the top must-see sights in St. Petersburg. ...
【简答题】When you go to St. Petersburg, the number of attractions can seem large. If you are short of time, or just want to make sure to hit the highlights , these are the top must-see sights in St．Petersburg．...
【判断题】压力铸造时,液态合金在压力作用下,可以铸造形状复杂的薄壁件。但由于铸型为金属材料制造,液态金属冷却速度快。铸件的内应力较砂型铸造高,因此通常需要进行去应力退火处理。
A.
正确
B.
错误
【简答题】A. Clearly there were changes in the ty pes of accommodation that studen ts opted for between the 1960 s and the 2000s. but the large in crease in the number of students living in shared accommodation...
【判断题】压力铸造时,可以铸造形状复杂的薄壁件。但由于铸型为金属铸型,液态金属冷却速度快。铸件的内应力较砂型铸造高,因此压力铸造的铸件通常需要进行去应力退火处理。 ( )
A.
正确
B.
错误
【判断题】压力铸造时,液态合金在压力作用下,可以铸造形状复杂的薄壁件。但由于铸型为金属材料制造,液态金属冷却速度快。铸件的内应力较砂型铸造高,因此通常需要进行去应力退火处理。
A.
正确
B.
错误
【简答题】He insisted that we all ____ in his office at one o'clock. A) be B) to be C) would be D) shall be
【单选题】During the Queen Elizabeth 1st ’s reign, the number of English speakers as first language was ( )
A.
5 to 7 billion
B.
4 to 6 million
C.
5 to 7 million
D.
4 to 6 billion
【单选题】The number of the members in the House from each state ______.
A.
is fixed, two from each state
B.
depends on how many people the state has
C.
depends on the size of the state
D.
depends on the location of the state
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