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【单选题】
日本宇宙航空研究开发机构发布的观测结果显示，北冰洋的海冰面积已经处于史上第二小，海冰密度处于史上最低的状态，海水间缝隙大小的指标也处于史上最低水平。近年来，石油和天然气等燃料的广泛使用，导致温室气体排放大幅增加，全球气候变暖，成为北极海冰融化的罪魁祸首。北极海底的永久冻土渐趋融化，也会释放出大量的甲烷等气体，反过来加剧全球温室效应。 这段文字最适合的标题是( )。A.
北冰洋海冰面积处于史上第二小
B.
温室气体增加全球气候变暖
C.
北极海底的永久冻土渐趋融化
D.
全球变暖致北极海冰密度处于史上最低
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反馈参考答案：
举一反三
【判断题】C0为通用计数器,只能进行加计数,当计数的当前值=设定值后,即使再有计数输入信号,计数器当前值保持为设定值不变。而C200为双向计数器,当为加计数工作时,当计数的当前值=设定值后,如再有计数输入信号,计数器当前值仍继续增加。
A.
正确
B.
错误
【多选题】Regarding an IPsec security association （SA）， which two statements are true？（）
A.
IKE SA is bidirectional.
B.
IPsec SA is bidirectional.
C.
IKE SA is established during phase 2 negotiations.
D.
IPsec SA is established during phase 2 negotiations.
【单选题】The two fishermen saw ___________ in the sky while they were fishing by a river.
A.
something strange
B.
anything strange
C.
strange something
D.
strange anything
【简答题】Once upon a time, there were two fishermen who were good at fishing. One day they went to a lake to . One of them fishing alone by himself the other was an outgoing person who loved to friends with di...
【单选题】Two fishermen saw ___in the sky while they were fishing by a lake.
A.
something strange
B.
anything strange
C.
strange something
D.
strange anything
【简答题】适航规章要求，化学氧气发生器应至少保证多长时间的供氧() A12分钟 B30分钟 C60分钟 D90分钟
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