An Exam Paper Contains the Following Equation for Rocket Propulsion $( M + \Delta m ) v = M ( v + \Delta v ) + \Delta m \left( v + v _ { e } \right)$

Multiple Choice

An exam paper contains the following equation for rocket propulsion: $( M + \Delta m ) v = M ( v + \Delta v ) + \Delta m \left( v + v _ { e } \right)$ . The error in the equation is that,instead of (v + v_e) ,the velocity of the fuel relative to the ground should be

A) -v_e.
B) +v_e.
C) v - v_e.
D) v_e-0 v.
E) 2v_e.