An object of mass $10 \mathrm{kg}$ is connected to the lower end of a massless string of length $4 \mathrm{m}$ hanging from the ceiling. If a force $F$ is applied horizontally at the mid-point of the string, the top half of the string makes an angle of $45°$ with the vertical, then the magnitude of $F$ is

• A

  $75 \mathrm{N}$
• B

  $90 \mathrm{N}$
• Correct answer
  C

  $100 \mathrm{N}$
• D

  $70 \mathrm{N}$

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