Two masses $A$ and $B$, each of mass $M$ are fixed together by a massless spring, A force acts on the mass $B$ as shown in figure. If the mass $A$ starts moving away from mass $B$ with acceleration $a$, then the acceleration of mass $B$ will be :

• A

  $\frac{MF}{F+Ma}$

• B

  $\frac{F+Ma}{M}$
• C

  $\frac{Ma-F}{M}$
• Correct answer
  D

  $\frac{F-Ma}{M}$

Hence, the correct answer is option: 'D'.