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【单选题】
生态系统各构成要素的不可缺少性,或构成要素有足够的数量以保证与各要素间优化协调的关系,实际上构成了生态系统的平衡与稳定。而生态平衡和生态稳定又是生态生产的必要形式,只有在这种形式或形态下,生态生产才具有最大生产力和最高生产量。以下哪项,从上述题干中推出最为恰当?A.
破坏了生态平衡,经济增长就会停滞。
B.
“人定胜天”,人类可以凭借高技术手段大量从自然界中摄取,而不会破坏生态平衡。
C.
生态系统有“自稳定机制”,能够实现自身的良性循环。
D.
要想扩大生态生产的数量、提高它的质量,必须维护生态系统的平衡和稳定。
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皮皮学刷刷变学霸
举一反三
【单选题】When you are dining with someone important and your cell phone rings, you:
A.
Answer it within two rings and keep the call brief
B.
Ignore it and pretend that someone else’s phone is ringing
C.
Apologize and turn the phone on silent mode. The person you’re with takes priority.
D.
Apologize, step away from the table, and take the call in the lobby or restroom.
【多选题】What are not expected to do when you are seated in a dining table?
A.
Take pills
B.
Use lipsticks
C.
Use cell phones
D.
Talking to guests on your left and right sides.
【单选题】When you are dining in a restaurant and you accidentally drop your fork on the floor, you:
A.
Pick it up, wipe it off, and use it anyway
B.
Pick it up, give it to the server, and ask him to bring you another one
C.
Leave it on the floor and ask the server to bring you another one
D.
Leave it on the floor and use your neighbor’s fork when he’s not looking
【简答题】net income
【简答题】变容二极管直接调频电路如图所示。图中Lc为高频扼流圈，C1、C4为隔直流耦合电容，C2、C3为高频旁路电容。
已知变容管的γ=2，V B =1V，C jQ =100PF，L 1 =100μH，调制电压为u Ω （t）=0.1cos2π×10 4 t（v）。 指出振荡电路类型；
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