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【单选题】
公路常用冲刷防护设备中属直接防护的有（ ）。A.
丁坝
B.
顺坝
C.
改河道
D.
浆砌块石挡土墙
拍照语音搜题，微信中搜索"皮皮学"使用
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参考解析：
知识点：
皮皮学刷刷变学霸
举一反三
【简答题】若3x等于5y，则x：y=______．
【单选题】The invisible hand usually leads markets to allocate resources efficiently.
A.
assign
B.
persuade
C.
ask
D.
order
【简答题】先化简，再求值： （1）若x=﹣1，y=0.5，则（x﹣5y）（﹣x﹣5y）﹣（﹣x+5y） 2 =（ ）； （2）若x=2，y=﹣3，则 =（ ）。
【单选题】When the "invisible hand" guides economic activity, prices of products reflect
A.
only the values that society places on those products.
B.
only the costs to society of producing those products.
C.
both the values that society places on those products and the costs to society of producing those products.
D.
none of the above; when the "invisible hand" guides economic activity, prices of products are set by the government in a manner that is thought to be "fair."
【单选题】The invisible hand of the marketplace acts to allocate resources
A.
fairly but does not necessarily ensure that resources are allocated efficiently.
B.
efficiently but does not necessarily ensure that resources are allocated fairly.
C.
both fairly and efficiently.
D.
neither fairly nor efficiently.
【单选题】宽带（宽频）探头，不包括下列含义
A.
发射很宽的频带，如2～5MHz范围
B.
接收所有频率，即2～12MHz回声，包括近远程
C.
接收所有频率限于中近程，远程只能接收较低频率
D.
在接收的回声中选择某一特定的中心频率
E.
近程取高频，中程取中频，远程按低频，即动态接收
【简答题】在许多情境中，行为与事件的发生并非由内因或外因单一因素引起，而兼有二者的影响。这种归因叫收（）。 (A)成败归因 (B)稳定归因 (C)综合归因 (D)不可控归因
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