Consider the Reaction -The Mass Balance Equation for Fractional Surface Coverage Of

Consider the reaction $$\begin{array} { l } M \stackrel { k _ { 1 } } { \longrightarrow } M _ { a ds } ^ { + } + e ^ { - } \\M + M _ { a d s } ^ { + } \stackrel { k _ { 2 } } { \longrightarrow } M _ { a d s } ^ { + } + M _ { s o l } ^ { + } + e ^ { - } \\M _ { a d s } ^ { + } \stackrel { k _ { s } } { \longrightarrow } M _ { s o l } ^ { + }\end{array}$$
-The mass balance equation for fractional surface coverage of $$M _ { a d s} ^ { + }$$
is given by

A) $$\Gamma \frac { d \theta } { d t } = k _ { 1 } ( 1 - \theta ) - k _ { 2 } \theta ( 1 - \theta ) + k _ { 3 } \theta$$
B) $$\Gamma \frac { d \theta } { d t } = k _ { 1 } ( 1 - \theta ) - k _ { 2 } \theta ( 1 - \theta )$$
C) $$\Gamma \frac { d \theta } { d t } = k _ { 1 } ( 1 - \theta ) - k _ { 2 } \theta ( 1 - \theta ) - k _ { 3 } \theta$$
D) $$\Gamma \frac { d \theta } { d t } = k _ { 1 } ( 1 - \theta ) - k _ { 3 } \theta$$