GMAT逻辑复习资料-逻辑大全分类-Must be true

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大全-19-11.        Naturally occurring chemicals cannot be newly patented once their structures have been published. Before a naturally occurring chemical compound can be used as a drug, however, it must be put through the same rigorous testing program as any synthetic compound, culminating in a published report detailing the chemical’s structure and observed effects.
culminate: =end, culminate in…
If the statements above are true, which of the following must also be true on the basis of them?
(A) Any naturally occurring chemical can be reproduced synthetically once its structure is known.
(B) Synthetically produced chemical compounds cannot be patented unless their chemical structures are made public.原文没提关于合成混合物的专利授予方式
(C) If proven no less effective, naturally occurring chemicals are to be preferred to synthetic compounds for use in drugs.
(D) Once a naturally occurring compound has been approved for use as a drug, it can no longer be newly patented.(D)
自然产生的化学品一旦其结构被公布，则不能以新的方式授予专利；在一种自然产生的化学品混合物被当成药物使用之前，它必须通过跟合成混合物一样的严格检验，最终才公布其化学结构的详细内容和被发现的效果。
先看后一句的信息，再结合第一句的内容，很容易发现D是对的，一但一种自然形成的化学混合物被证明是药，它的化学结构一定是被公布了的，而一但公布化学结构，就不能以授予新专利了。。ABC都是无关选项了。。只有E有点绕。。“一种自然形成的化学品不能被授予新的专利，除非它的作为药的效果被严格检验”。。显然这于文中能形成的推导正好相反。
(E) A naturally occurring chemical cannot be patented unless its effectiveness as a drug has been rigorously established.
凡是这种“不能...除非...”的题，建议大家都想成“能...如果....”

大豆

大全-10-18.        There are fundamentally two possible changes in an economy that will each cause inflation unless other compensating changes also occur. These changes are either reductions in the supply of goods and services or increases in demand. In a prebanking economy the quantity of money available, and hence the level of demand, is equivalent to the quantity of gold available.
If the statements above are true, then it is also true that in a prebanking economy
(A) any inflation is the result of reductions in the supply of goods and services
(B) if other factors in the economy are unchanged, increasing the quantity of gold available will lead to inflation
在prebanking economy，demand=gold available，因此gold增多就等于demand增多，可以导致inflation。
(C) if there is a reduction in the quantity of gold available, then, other things being equal, inflation must result
(D) the quantity of goods and services purchasable by a given amount of gold is constant
(E) whatever changes in demand occur, there will be compensating changes in the supply of goods and services

大豆

大全-12-14.        The most important aspect of moviemaking is conveying a scene’s rhythm. Conveying rhythm depends less on the artistic quality of the individual photographic images than on how the shots go together and the order in which they highlight different aspects of the action taking place in front of the camera.
If the statements above are true, which of the following must be true on the basis of them?
(A) The artistic quality of the individual photographic image is unimportant in movie photography.
(B) Photographers known for the superb artistic quality of their photographs are seldom effective as moviemakers.
(C) Having the ability to produce photographs of superb artistic quality does not in itself guarantee having the ability to be a good moviemaker.
(D) Movie photographers who are good at their jobs rarely give serious thought to the artistic quality of the photographs they take.
(E) To convey a scene’s rhythm effectively, a moviemaker must highlight many different aspects of the action taking place.

大豆

大全-12-2.        Consumer income reports produced by the government distinguish between households and families by means of the following definition: “A family is a household containing a householder and at least one person related to the householder.” Except for the homeless and people in group living quarters, most people live in households.
According to the definition above, which of the following must be true?
(A) All householders are members of families.
(B) All families include a householder.
(C) All of the people related to a householder form a family.
(D) Some people residing in group living quarters are members of families.
(E) Some homeless people reside in group living quarters.

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大全-18-12.Holiday receipts—the total sales recorded in the fourth quarter of the year—determine the economic success or failure of many retail businesses. Camco, a retailer selling just one camera model, is an excellent example. Camco’s holiday receipts, on average, account for a third of its yearly total receipts and about half of its yearly profits.这句话是重点,收入占全年的1/3,利润占全年的1/2.
If the statements above are true, which of the following must also be true about Camco on the basis of them?
(A) Its fixed expenses per camera sold are higher during the fourth quarter than for any of the other three quarters.
(B) It makes more profit during the first and third quarters combined than during the fourth quarter.
(C) Its per-camera retail price is lower, on average, during the fourth quarter than during any one of the first three quarters.
(D) It makes less profit, on average, for a given dollar amount of sales during the first three quarters combined than during the fourth quarter.(D)
第四季度的收入占全年的1/3,但利润却占全年的1/2,第一至三季度的收入占全年的2/3,利润占全年1/2.
相同的销量比较,第四季度比前三季度的平均利润要高.
(E) The per-camera price it pays to wholesalers is higher, on average, during the fourth quarter than during any of the other three quarters.原文只谈到receipts和profits,没有谈到价格.