一、先读问题 二、再读文章 三、再看选项
if A then B 表示A充分的推出B(A→B);
only if A then B 表示只有A才有B( B→A);
规则：和only if 最接近的元素一定是必要条件，是箭头所指方向。
by A in order to B 表示A 推出B(A→B);
must by A in order to B 表示B 推出A( B→A);
If only A, then B表示只有A才有B( A→B);
Not A, unless B表示没有A 除非有B(A→B);
A, unless B表示非B推出A或者非A推出B( →A, →B);
A require B表示B是A的必要条件(A→B);
A is necessary to B表示A是B成立的必需(B→A);
A depend/draw/base on B表示B是A成立的必需(A→B)。
例2.To be mentally healthy, people must have self-respect. People can maintain self-respect only by continually earning the respect of others they esteem. They can earn this respect only by treating these others morally.
Which of the following conclusions can be properly drawn from the statements above?
(A) People who are mentally healthy will be treated morally by others.
(B) People who are mentally healthy will have treated morally those they esteem.
(C) People who are mentally healthy must have self-respect in other to be treated morally by others.
(D) People can expect to be treated morally by others only if they esteem these others.
(E) People who have self-respect seldom treat morally those esteem.
例3. Most television viewers estimate how frequently a particular type of accident or crime occurs by how extensively it is discussed on television news shows. Television news shows report more on stories that include dramatic pictures such as fires and motor vehicle accidents than they do on more common stories that have little visual drama such as bookkeeping fraud.
If the statements above are true, it can be properly concluded that which of the following is also true?
(A) The time television news reporters spend researching news stories is directly related to the number of viewers who will be affected by events like those in the news stories.
(B) It is easier for crimes such as bookkeeping fraud to go unprosecuted than it is crimes such as arson.
(C) The number of fires and motor vehicle accidents greatly increases after each television news show that includes dramatic pictures of a fire or motor vehicle accident.
(D) Viewers of television news show tend to overestimate the number of fires and motor vehicle accidents that occur relative to the number of crimes of bookkeeping fraud.
(E) The usual selection of news stories for television news show is determined by the number of news reporters available for assignment.