新GRE阅读36套解析Execrise8.docx

Exercise 8Heat pumps circulate a fluid refrigerant制冷剂 that cycles alternatively from its liquid phase to its vapor phase in a closed loop闭合环路. The refrigerant, starting as a lowtemperature, low-pressure vapor, enters a compressor压缩机driven by an electric motor. The refrigerant leaves the compressor as a hot, dense vapor and flows through a heat exchanger called the condenser冷凝剂, which transfers heat from the refrigerant to a body of air. Now the refrigerant, as a high-pressure, cooled liquid, confrontsa flow restriction which causes the pressure to drop. As the pressure falls, the refrigerant expands and partially vaporizes, becoming chilled. It then passes through a second heat exchanger, the evaporator, which transfers heat from the air to the refrigerant, reducing thetemperature of this second body of air.(126 words)1. According to the passage, the role of the flowrestriction in a heat pump is to(A) measure accurately the flow rate of therefrigerant mass at that point(B) compress and heat the refrigerant vapor(C) bring about the evaporation and cooling ofrefrigerant【Now the refrigerant, as a high-pressure, cooled liquid, confronts10 a flow restriction which causes the pressure to drop. As the pressure falls, the refrigerant expands and partially vaporizes, becoming chilled.】(D) exchange heat between the refrigerant and theair at that point(E) reverse the direction of refrigerant flow whenneededTraditionally, the study of history has had fixed boundaries and focal焦点 points—periods, countries, dramatic events, and great leaders. It also has had clearand firm notions of scholarly procedure: how oneinquires into a historical problem, how one presents and documents one‘s findings, what constitutes admissible可被采纳，可被接受的 and adequate proof.The recent popular psychohistory, committed to Freudian psychoanalysis, takes a radically different approach. This commitment precludes排除了 acommitment to history as historians have always understood it. Psychohistory derives its ―facts‖