Question

The regular expressions denote zero or more instances of an x or y is?

(a) (x+y)

(b) (x+y)*

(c) (x* + y)

(d) (xy)*

I had been asked this question in a job interview.

The origin of the question is Finite Automata and Regular Expressions topic in division Compiler Introduction of Compiler

Answer 1

The correct choice is (b) (x+y)*

To explain I would say: For instances of x or y the exp is x+y and both can zero or more times than (x+y)*.