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## Answer Key and Solved Questions Paper-3 UGC-NET Computer Science December 2015

21. Let n=4 and (a1, a2, a3, a4) = (do, if, int, while). Let p(1:4) = (3/8, 3/8, 1/8, 1/8) and q(1:4) = (2/8, 3/8, 1/8, 1/8, 1/8) where p(i) and q(i) denotes the probability with which we search ai and the identifier x being searched satisfy ai < x < ai+1 respectively. The optimal search tree is given by:
A.
B.
C.
D.
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22.The family of context sensitive languages is ................. under union and ................. under reversal.
A.closed, not closed
B.not closed, not closed
C.closed, closed
D.not closed, closed
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23.Match the following :
 List - I List - II (a) {an bn|n > 0} is a deterministic (i) but not recursive language context free language (b) The complement of {an bn an|n > 0} (ii) but not context free language is a context free language (c) {an bn an} is context sensitive language (iii) but can not be accepted by a deterministic pushdown automation (d) L is a recursive language (iv) but not regular

Codes :
(a) (b) (c) (d)
A.(i) (ii) (iii) (iv)
B.(i) (ii) (iv) (iii)
C.(iv) (iii) (ii) (i)
D.(iv) (iii) (i) (ii)
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24.The language of all non-null strings of a’s can be defined by a context free grammar as follow :
S-->a S|S a| a
The word a3 can be generated by ................ different trees.
A.Two
B.Three
C.Four
D.Five
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25.Which one of the following non-functional quality attributes is not highly affected by the architecture of the software ?
A.Performance
B. Reliability
C.Usability
D.Portability
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26.The context free grammar given by
S-->XYX
X-->aX|bX|?
Y-->bbb
generates the language which is defined by regular expression:
A.(a+b)*bbb
B.abbb(a+b)*
C.(a+b)*(bbb)(a+b)*
D.(a+b)(bbb)(a+b)*
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27.There are exactly ................ different finite automata with three states x, y and z over the alphabet {a, b} where x is always the start state.
A.64
B.256
C.1024
D.5832
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28.Given the following two languages : L1={anban|n>0} L2={anbanbn+1|n>0} Which of the following is correct?
A.L1 is context free language and L2 is not context free language
B.L1 is not context free language and L2 is context free language
C.Both L1 and L2 are context free languages
D.Both L1 and L2 are not context free languages
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29.Which of the following is used to make an Abstract class ?
A.Making atleast one member function as pure virtual function
B.Making atleast one member function as virtual function
C.Declaring as Abstract class using virtual keyword
D.Declaring as Abstract class using static keyword
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30.Match the following with reference to object oriented modelling :
 List - I List - II (a) Polymorphism (i) Picking both operator and attributes with operations appropriate to model an object (b) Inheritance (ii) Hiding implementation details of methods from users of objects (c) Encapsulation (iii) Using similar operations to do similar things (d) Abstraction (iv) Create new classes from existing class
Codes :
(a) (b) (c) (d)
A.(iv) (iii) (i) (ii)
B.(iii) (iv) (i) (ii)
C.(iii) (i) (ii) (iv)
D.(iv) (iii) (ii) (i)
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Author Does Not claim of any answer these answers are as per expert opinion

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