# Regular expressions MCQs [Theory of automata]

## Regular expressions MCQs in Theory of automata

Regular expressions are closed under
(a) Union
(b) Intersection
(c) Kleen star
(d) none of these

(e) All of these

(e) All of these

Which strings are valid for Regular Expression aa(bb)*
a. bb, bbbb, bbbbbb,…
b. abb, abbbb, abbbbbb,…
c.  aabb, aabbbb, aabbb,…
d.  aabb, aabbbb, aabbbb,…

aabb, aabbbb, aabbbb,…

Regular Expression For All Strings Starts With a defined over {a,b}
a. a(a+b)
b. a(a+b)*

c.  a*

d.  a*(a+b)*

b. a(a+b)*

Regular Expression For All Strings Starts With ab and ends with b defined over {a,b}
a. ab(a+b)b
b. ab(a+b)* b

c.  ab* b

d.  None of these

ab(a+b)* b

Regular Expression For All Strings having always consecutive a’s defined over {a,b}
a.  (aa+b)
b.  aa(b)*
c.  (aa+b)*
d.  None of these

c.  (aa+b)*

Which one is correct regarding Regular Expression?
a.  We can draw FA for each regular expression

b. We can’t draw FA for some regular expression
c.  RE defines regular languages
d.  Both a and C