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【单选题】
下面关于海洋污染的基本特征描述不正确的是A.
污染来源广、数量大，成分复杂
B.
海洋污染影响范围大
C.
海洋污染持续性强，危害大
D.
由于海洋具有自净能力，所以海洋污染治理（清理）比较简单
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举一反三
【单选题】A message signal can any amplitude value between 0 and A volts.
A.
assume
B.
use
C.
receive
D.
accept
【简答题】How to Make Smiley Faces Including emoticons in your text messages is a way for you to express your feelings or signal the topic of your text Using the right emoticon can help your reader gain a bette...
【简答题】How to Make Smiley Faces Including emoticons in your text messages is a way for you to express your feelings or signal the topic of your text. Using the right emoticon can help your reader gain a bett...
【多选题】Explain why a cell’s response to a signal can be fast or slow.
A.
The length of time a cell takes to respond to an extracellular signal can vary greatly, depending on what needs to happen once the message has been received.
B.
Some extracellular signals act swiftly: acetylcholine can stimulate a skeletal muscle cell to contract within milliseconds and a salivary gland cell to secrete within a minute or so. Such rapid responses are possible because, in each case, the signal affects the activity of proteins that are already present inside the target cell, awaiting their marching orders.
C.
Other responses take more time. Cell growth and cell division, when triggered by the appropriate signal molecules, can take many hours to execute.
D.
This is because the response to these extracellular signals requires changes in gene expression and the production of new proteins.
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