10.which of the following can be the order of lectures
and lunch at the conference？
（a） w， x， lunch， y， s， t， z
（b） x， y， t， lunch， s， z， w
（c） y， t， lunch， s， w， x， z
（d） z， t， w， s， lunch， y， x
（e） z， w， y， s， lunch， x， t
11.if exactly two lectures are given before lunch， they
must be
（a） x and t
（b） y and t
（c） z and t
（d） z and w
（e） z and y
12.if exactly three lectures， including y and z， are given
before lunch， which of the following can be true？
（a） t is the second lecture.
（b） t is the fifth lecture.
（c） w is the third lecture.
（d） x is the first lecture.
（e） x is the third lecture.
13.if t is the sixth lecture， which of the following must
be true？
（a） x is the first lecture.
（b） x is the second lecture.
（c） exactly two lectures are given before lunch.
（d） exactly three lectures are given before lunch.
（e） exactly four lectures are given before lunch.
14.if s and z are both given after lunch， which of the
following must be true？
（a） x is given before lunch.
（b） x is given after lunch.
（c） y is given before lunch.
（d） t is the third lecture.
（e） z is the fifth lecture.
15.which of the following lectures cannot be given
immediately before lunch？
（a） s
（b） t
（c） x
（d） y
（e） z
questions 16-22
a circus has seven fenced enclosures， numbered 1 through
7， for two animals： a lion and a tiger. each enclosure is
connected to adjacent enclosures by interior gates. there
are exactly eight such gates， each connecting one enclosure to exactly one other enclosure： enclosure 1 is connected to enclosures 2， 3 and 4； enclosure 3 to enclosures 1， 2， 4， and 5； and enclosure 5 to enclosures 3， 6， and 7. these gates provide the only connections between enclosures. occasionally a trainer moves the animals. taking either animals from one enclosure to an adjacent enclosure through a gate is called a “transfer.” the following conditions are strictly observed：
the two animals cannot be together in any enclosure or
gate.
transfers cannot occur simultaneously
in moving either one animal or both to a specified
enclosure or enclosures， the minimum number of trans-
fers needed to achieve the specified result are used.
16.if the lion is in enclosure 1 and the tiger is in enclo-
sure 3， and the lion is to be moved to enclosure 7， the
tiger could be in which of the following enclosures
when all of the transfers have been completed？
（a） 1
（b） 3
（c） 4
（d） 5
（e） 6