GRE北美题No4-2.doc

No. 4-1 SECTION 3
Questions 1-7
A certain code uses only the letters K, L, M, N, and
O. Words in the code are written from left to right.
Code words are only those words that conform to the
following conditions:
The minimum length for code words is two letters,
not necessarily different from each other.
K cannot be the first letter in a word.
L must occur more than once in a word, if it
occurs at all.
M cannot be the last letter in a word, nor the
next-to-the-last letter.
N must occur in a word if K occurs in the word.
O cannot be the last letter in a word unless
L occurs in the word.
1. Which of the following letters could be placed
after O in L O to form a code word exactly
three letters long?
(A) K (B) L (C) M (D) N (E) O
2. If the only kinds of letters that are available
are K, L, and M, then the total number of
different code words, each exactly two letters
long, that it is possible to make is
(A) 1 (B) 3 (C) 6 (D) 9 (E) 12
3. Which of the following is a code word?
(A) K L L N (B) L O M L (C) M L L O
(D) N M K O (E) O N K M
4. What is the total number of different code words
exactly three identical letters long that it is
possible to make?
(A) 1 (B) 2 (C) 3 (D) 4 (E) 5
5. The code word M M L L O K N can be
turned into another code word by carrying out
any one of the following changes EXCEPT
(A) replacing every L with an N
(B) replacing the first M with an O
(C) replacing the N with an O
(D) moving the O to the immediate right of
the N
(E) moving the second L to the immediate left
of the K
6. Which of the following is not a code word but
could be turned into one by changing the order
of the letters within the word?
(A) K L M N O (B) L L L K N
(C) M K N O N (D) N K L M L
(E) O M M L L
7. Which of the following could be turned into a
code word by replacing the “X” with a letter
used in the code?
(A) M K X N O (B) M X K M N
(C) X M M K O (D) X M O L K
(E)