What kind of clauses are available in Conjunctive Normal Form? A. Disjunction of literals B. Disjunction of variables C. Conjunction of literals D. Conjunction of variables

The correct answer is: C. Conjunction of literals

A clause in conjunctive normal form (CNF) is a disjunction of literals. A literal is a variable or its negation.

For example, the following are clauses in CNF:

• $x \lor \neg y$
• $\neg x \lor y$
• $x \lor y \lor z$

The following are not clauses in CNF:

• $x$
• $\neg x$
• $x \land y$

A formula in CNF is a conjunction of clauses. For example, the following formula is in CNF:

• $(x \lor \neg y) \land (\neg x \lor y) \land (x \lor y \lor z)$

A formula is in CNF if and only if it can be written as a conjunction of clauses, where each clause is a disjunction of literals.