questions 18-23
seven lights-j，k，l，m，n，o，and p-have only two possible settings：on or off.they are arranged on a particular electric circuit as follows.
if k is on，l is off;if k is off，l is on.
j and n cannot both be on.
if m is off，either j or n is on;if either j or n is on，m is off.
if p is on，l is on.
if o is off，n is off;if o is on，n is on.
assume that the circuit is working as designed.
18.any of the following can be true except:
(a) j and o are both off.
(b) k and n are both off.
(c) k and p are both on.
(d) l and m are both on.
(e) n and o are both on.
19.if l and o are on，which one of the following must be true?
(a) j is and k is off.
(b) j is off and n is on.
(c) k is off and m is on.
(d) k is off and p is on.
(e) m is off and p is on.
20.which one of the following can be true?
(a) only j，k，and m are off.
(b) only j，l，and m are off.
(c) only k，m，and o are off.
(d) only l，n，and o are off.
(e) only m，n，and o are off.
21.if p is on，what is the maximum number of lights that can be off?
(a) 2
(b) 3
(c) 4
(d) 5
(e) 6
22.what is the minimum number of lights that must be on?
(a) 0
(b) 1
(c) 2
(d) 3
(e) 4
23.if j is on，which one of the following could be a complete and accurate list of the remaining lights that are also on?
(a) k，l，and m
(b) l，n，and p
(c) l，o，and p
(d) m，n，and o
(e) l and p
答案：d e c e d d d d a e e e a d e c a b d b b d d
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