De-Morgan'w theorem is

• A. \(\rm \overline{\bar{A}+\bar{B}}=\bar{A}\cdot \bar{B}\)
• B. \(\rm \overline{A\cdot B}=\bar{A}+\bar{B}\)
• C. \(\rm \bar{A}-\bar{B}=\bar{A}\cdot \bar{B}\)
• D. \(\rm \bar{B}\cdot \bar{A}=\bar{A}+\bar{B}\)