There are two logic operations: conjunction (logic AND) and disjunction (logic OR).

Question

There are two logic operations: conjunction (logic AND) and disjunction (logic OR).

Accepted Answer

Can not be proved since it is the  3rd  postulate.

Answer

It must be proved since it is a theorem of the Boole-algebra.

Answer

Can not be proved since it is the   4th  postulate.

Answer

It can be proved since it is a consequence of the postulates.

Crowdly