  We review and develop the formalism of ghost number cohomologies, outlined in
our previous work, to classify the quantum states of M-theory. We apply this
formalism to the matrix formulation of M-theory to obtain NSR superstring
action from dimensionally reduced matrix model. The BPS condition of the matrix
theory is related to the worldsheet reparametrizational invariance in
superstring theory, underlining the connection between unbroken supersymmetries
in M-theory and superstring gauge symmetries.
