What should be done to obtain an OR gate from a NAND gate?

• A. We need only 3 NAND gates
• B. We need two NOT gates obtained from NAND gates and one NAND gate
• C. We need 3 NOT gates obtained from NAND gates and 3 NAND gates
• D. We need 2 NAND gates and 4 AND gates obtained from NAND gates.