why a capacitor and inductor cannot work with d.c?

An inductor can work with dc. An ideal inductor behaves simply as a piece of wire placed in the circuit. It will not impede the flow of current in any way.

 The plates of the capacitor get charged and then further flow of current in the circuit stops.When a capacitor is placed in the circuit current cannot flow right through it.

An ideal inductor(zero resistance) allows dc to pass through but it blocks ac.

This can also be understood from the expression for inductive reactance and capacitive reactance also.