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问题 选择题
在复平面内复数（1+bi）（2+i）（i是虚数单位，b是实数）表示的点在第四象限，则b的取值范围是（　　）
A．b＜-
1
2
B．b＞-
1
2
C．-
1
2
＜b＜2		D．b＜2
答案

∵（1+bi）（2+i）=2-b+（1+2b）i

复数（1+bi）（2+i）（其中i为虚数单位）在复平面内对应的点位于第四象限，

则

2-b＞0
1+2b＜0

∴b＜-

1
2

则b的取值范围是b＜-

1
2
．

故选A．

填空题

Some consumer researchers distinguish_____(1) "rational" motives and "emotional" (or "non-rational") motives. They use the term "rationality"_____(2) the traditional economic sense that assumes_____(3) consumers behave rationally when they carefully consider all alternatives_____(4) choose those that give them the greatest utility (i.e., satisfaction). _____(5) a marketing context, the term "rationality" implies that the consumer selects goods based_____(6) totally objective criteria, such_____(7) size, weight, price, and so on. "Emotional" motives imply the selection of goods____(8) to personal or subjective criteria — the desire_____(9) individuality, pride, fear, affection or status.The assumption underlying this distinction is____(10) subjective or emotional criteria do not maximize utility or satisfaction. _____ (11), it is reasonable to assume that consumers always attempt to select alternatives that, ____(12) their view, serve to maximize satisfaction. Obviously, the assessment of satisfaction is a very personal process, based_____(13) the individual’’s own needs as_____(14) as on past behavioral, social, and learning experiences. What may appear_____(15) irrational to an outside observer may be perfectly rational ______(16) the context of the consumer’’s own psychological field. For example, a product purchased to enhance one’’s self-image (such as a fragrance) is a perfectly rational form of consumer behavior. ____(17) behavior did not appear rational to the person who undertakes it_____ (18) the time that it is undertaken, obviously he or she would not do it._____(19) the distinction between rational and emotional motives does not appear to be warranted.Some researchers go so far_____(20) to suggest that emphasis_____ (21) "needs" obscures the rational, or conscious, nature of most consumer motivation. They claim that con sumers act consciously____(22) maximize their gains and minimize their losses; that they act not____(23) subconscious drives but from rational preferences,____(24) what they perceive to be_____(25) their own best interests.
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选择题

保持五氧化二磷化学性质的最小粒子是（　　）

A．磷原子

B．氧原子

C．磷原子和氧原子

D．五氧化二磷分子
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