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【单选题】
下列关于生态系统稳定性的叙述,正确的是( ) 1反馈调节是生态系统自我调节的基础 2“遭到破坏,恢复原状”属于生态系统的抵抗力稳定性 3人们对自然生态系统的“干扰”不能超过其抵抗力稳定性 4热带雨林在遭到严重的砍伐后,其恢复力稳定性仍很强 A.14 B.12 C.13 D.23A.
1
B.
2
C.
3
D.
4
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【单选题】听力原文： In a police station, an officer managed to get some fresh mushrooms. He was so happy that he agreed to share the mushrooms. When their breakfast arrived the next day, each officer found some mus...
A.
He was so pleased that he wanted to share the mushroom with it.
B.
The dog would enjoy the mushroom.
C.
He liked the dog very much.
D.
He was afraid of mushroom poisoning and wanted to test the mushroom by the dog.
【简答题】预应力连续梁桥的施工方法有______、装配一整体施工、______、______和移动式模架逐孔施工。
【单选题】氟尿嘧啶是 胸腺嘧啶核苷酸合成酶抑制剂,是 用氟原子取代尿嘧啶5-位氢原子得到,其原因是( )
A.
氟的毒性大，氟尿嘧啶比正常尿嘧啶对肿瘤细胞的毒性大
B.
氟原子的电负性大，氟尿嘧啶的嘧啶环电子云密度比正常尿嘧啶小
C.
氟的原子半径和氢的原子半径相近，氟尿嘧啶与正常尿嘧啶体积几乎相等，而且C-F键特别稳定
D.
氟原子的氧化性强，氟尿嘧啶会对NDA链产生氧化破坏
E.
氟尿嘧啶比正常尿嘧啶脂溶性强，更易进入肿瘤细胞内
【简答题】one day a police officer managed to get some fresh mushrooms( 蘑菇). he was so (1) what he had bought that he offered to(2 )the mushrooms with his brother officers. when their breakfast arrived the next...
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