美国GRE考试试题:美国GRE北美试题20（4）
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　　美国GRE考试试题:美国GRE北美试题20（4）

　　No. 5-1 SECTION 6

　　Questions 1-5

　　Because of a computer malfunction, an accountant cannot directly determine the classification of certain accounts. Each account falls into one of five classifica- tions: type 1, type 2, type 3, type 4, or type 5. The accountant hopes to be able to determine the classifica- tion of these accounts by tracing which operations the computer has performed on them. There are exactly four operations: W, X, Y, and Z. No operation can be performed more than once on a given account, and the operations were performed, without exception, according to the following rules:

　　If an account is a type 1, the computer performs either operation W or, alternatively, opera- tion X.

　　If the account is a type 2, the computer performs either operation X alone or, alternatively, opera- tion X and any one of the remaining operations except W.

　　If an account is a type 3, the computer performs either operation Y alone or, alternatively, opera- tion Y and one of the remaining operations

　　If an account is a type 4, the computer performs exactly two operations in any combination except that X cannot be one of the two operations.

　　If an account is a type 5, the computer performs exactly three operations in any combination drawn from the four operations.

　　1. If the accountant knows that the computer has per- formed exactly one operation on an account, which of the following must be true?

　　(A) The account is either a type 1 or a type 2.

　　(B) The account is either a type 1, type 2, or a type 3.

　　(C) The account is either a type 2, a type 3, or a type 5.

　　(D) The account is either a type 2, a type 4, or a type 5.

　　(E) The account is either a type 3, a type 4, or a type 5.

　　2. If the accountant knows that the computer has performed operation Z on an account but cannot determine solely from traces in the account whether any other operation has been performed, the account could be any one of the five types EXCEPT type

　　(A) 1 (B) 2 (C) 3 (D) 4 (E) 5

　　3. Which type of account, if operated on by the com- puter, must have operation X performed on it?

　　(A) Type 1 (B) Type 2 (C) Type 3

　　(D) Type 4 (E) Type 5

　　4. If the accountant knows that operations X and Z are the only operations that have been per- formed on an account, the account must be a type

　　(A) 1 (B) 2 (C) 3 (D) 4 (E) 5

　　5. If the accountant knows that the computer has per- formed exactly two operations on a given account, and operation Y was not one of the two, which of the following must be true?

　　(A) The account is either a type 1 or a type 2.

　　(B) The account is either a type 2 or a type 3.

　　(C) The account is either a type 2 or a type 4.

　　(D) The account is either a type 3 or a type 4.

　　(E) The account is either a type 3 or a type 5.