结合黄河流域示意图，回答问题。
小题1:黄河流域的开发应贯彻的方针应该是
A．把矿产资源的开发放在首位
B．植树造林，恢复植被
C．结合流域内的自然资源条件综合开发
D．水能开发必须是梯级开发小题2:影响黄河中游地区开发方向的最主要因素
A．气候条件
B．地形条件
C．水文特征
D．矿产资源小题3:黄河上游建设大型水电站的有利条件包括
①海拔高度大 ②河流流量大 ③水位季节变化大 ④地势落差大
A．①③
B．①④
C．②③
D．②④
小题1:C
小题2:D
小题3:D
小题1:流域的综合开发，根据流域的自然背景，因地制宜开发。选择C项。
小题2:黄河中游位于黄土高原地区，山西、陕西有丰富的煤炭资源，所以开发方向是矿产。选择D项。
小题3:水能的条件：一、流量大小；二、地形的落差大小。选择D项。
Most people give little thought to the pens they write with, especially since the printers in modern homes and offices mean that very 小题1: things are hand written. All too often, people buy a pen based only on 小题2:, and wonder why they are not satisfied 小题3: they begin to use it. However, buying a pen that you’ll enjoy is not 小题4: if you keep the following in mind. First of all, a pen should fit comfortably in your hand and be 小题5: to use. The thickness of the pen is the most important characteristic 小题6: comfort. Having a small hand and thick fingers, you may be comfortable with a thin pen. If you have a 小题7: hand and thicker fingers, you may 小题8: a fatter pen. The length of a pen can 小题9: influence comfort. A pen that is too 小题10: can easily feel top-heavy and unstable. Then, the writing point of the pen should 小题11: the ink to flow evenly（均匀地）while the pen remains in touch with the paper. 小题12: will make it possible for you to create a 小题13: line of writing. The point should also be sensitive enough to 小题14: ink from running when the pen is lifted. A point that does not block the 小题15: may leave drops of ink, 小题16: you pick the pen up and put it down again. 小题17:, the pen should make a thick, dark line. Fine-line pens may 小题18: bad handwriting, but fine lines do not command 小题19: next to printed text, as, 小题20: , a signature on a printed letter. A broader line, on the other hand, gives an impression of confidence and authority（权威）.
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