The binary operation ◻ is defined as follows:

Which one of the following is equivalence to $$P \vee Q$$?

For the compositive table of a cyclic group shown below

Which one of the following choices is correct?

What is the chromatic number of an $$n$$-vertex simple connected graph which does not contain any odd length cycle? Assume $$n \ge 2$$.

Which one of the following is TRUE for any simple connected undirected graph with more than $$2$$ vertices?