What is the negation of: Ram is in class X or Rashmi is in class XII?

Question

$\begin {array} {1 1} (A)\;Ram\: is\: not\: in\: class \: X \: and\: Rashmi\: is\: not\: in\: class\: XII. \\ (B)\;Ram\: is\: not\: in\: class\: X\: but\: Rashmi \: is\: in\: class\: XII. \\ (C)\;Either\: Ram \: is \: not \: in\: class\: X\: or \: Rashmi \: is\: not\: in \: class\: XII \\ (D)\;None\: of \: the \: above \end {array}$