1. Which of the following statements is incorrect? (a) An example of regular expressions is (a-b+c)´d. (b) Regular expressions are themselves strings of symbols. (c) A regular expression consists of three basic elements.(d) A regular expression is composed of three distinct operations.

2. Which of the following statements about regular expression operations is incorrect? (a) e is the annihilator for union.(b) f is the annihilator for concatenation. (c) f is the identity for union. (d) e is the identity for concatenation.

3. Which of the following statements is incorrect? (a) There exists an NFA whose language cannot be represented by a regular expression.(b) Every language accepted by a DFA may be represented by a regular expression. (c) Every language represented by a regular expression may be accepted by an NFA with epsilon-transitions. (d) The language expressing power of the regular expression is no better and no worse than the language accepting power of the automaton.

4. Which of the following statements is incorrect? (a) A regular expression is a human facial expression which is regular in style. (b) The regular expression is a kind of generator for strings of symbols. (c) Regular expressions define all and only regular languages. (d) Regular expressions may be used as commands for finding strings in web browsers.

5. Which of the following is identical to the regular expression a+bc*? (a) a+(b(c*)) (b) a+(bc)* (c) (a+bc)* (d) (a+b)c*