Mark the following statements as either True or False.

a$)($P $$ Q $$ R$)($P $$ S$)($E $$ F $$ G $$ H$)($I $$ J$)($K $$L$)$ is in conjunctive normal form $($CNF$).$

b$)$ The Law of Excluded Middle states that every proposition must be either true or false. c$)$ A $($B $$ C$)$ is semantically equivalent to $$C $($B $$A$).$

d$)$ Consider the following logical argument:

All online systems require internet connectivity to function properly.

The library catalog system is an online system.

Therefore, the library catalog system requires internet connectivity to function properly.

Note: The above logical argument is an example of the application of the modus tollens rule.