The block is placed on a frictionless surface in gravity free space. A heavy string of a mass m is connected and force F is applied on the string, then the tension at the middle of rope is 

• A

  $\frac{\left(\frac{\mathrm{m}}{2}+\mathrm{M}\right)\cdot \mathrm{F}}{\mathrm{m}+\mathrm{M}}$

• B

  $\frac{\left(\frac{\mathrm{M}}{2}+\mathrm{m}\right)\cdot \mathrm{F}}{\mathrm{m}+\mathrm{M}}$

• C

  zero

• D

  $\frac{\mathrm{M}\cdot \mathrm{F}}{\mathrm{m}+\mathrm{M}}$