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【单选题】
1931 年日本发动(),执行的不抵抗政策,使得东北三省迅速沦亡。A.
九一八事变
B.
华北事变
C.
卢沟桥事变
D.
四一二事变
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参考解析：
知识点：
皮皮学刷刷变学霸
举一反三
【单选题】拖拉机履带板和挖掘机铲齿受到严重的磨损及强烈冲击,应选用( )。
A.
W18Cr4V 淬火+低温回火
B.
ZGMn13 水韧处理
C.
GCr15 淬火+低温回火
D.
20Cr 渗碳+淬火+低温回火
【简答题】拖拉机和坦克履带板受到严重的磨损及强烈的冲击，应选用( )钢，采用( )处理。
【简答题】窗的开启方式有 、 、 、 、 等。
【多选题】What are the functions of actin filaments?
A.
Actin filaments, polymers of the protein actin, are present in most eukaryotic cells and are essential for many of the cell’s movements, especially those involving the cell surface. Without actin filaments, for example, an animal cell could not crawl along a surface, engulf a large particle by phagocytosis, or divide in two.
B.
Like microtubules, many actin filaments are unstable, but by associating with other proteins they can also form stable structures in cells, such as the contractile apparatus of muscle cells. Actin filaments interact with a large number of actin-binding proteins that enable the filaments to serve a variety of functions in cells.
C.
Depending on which of these proteins they associate with, actin filaments can form stiff and stable structures, such as the microvilli on the epithelial cells lining the intestine or the small contractile bundles that can contract and act like tiny muscles in most animal cells .
D.
They can also form temporary structures, such as the dynamic protrusions formed at the leading edge of a crawling cell or the contractile ring that pinches the cytoplasm in two when an animal cell divides. Actin-dependent movements usually require actin’s association with a motor protein called myosin.
【简答题】《中央关于加强党的执政能力建设的决定》是党的()届四中全会通过的。
【单选题】What is the cardiac sphincter for?
A.
it helps to move food along the oesophagus
B.
it helps to prevent food passing back up the oesophagus
C.
it's important in controlling stomach movements
【单选题】坦克和拖拉机履带板受到严重的磨损及强烈冲击，应选用
A.
20Cr渗碳后低温回火
B.
ZGMn13-3经水韧处理
C.
W18Cr4V淬火后低温回火
D.
Cr12经锻造处理
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