A girl holds a book of mass $\mathrm{m}$ against a vertical wall with a horizontal force $\mathrm{F}$ using heer fingér so that the book does not move. The frictional force on the book by the wall is $-$

• A

  $\mathrm{F}$ and along the finger but pointing towards the girl
• B

  $\mu \mathrm{F}$ upwards where $\mu$ is the coefficient of static friction
• Correct answer
  C

  $\mathrm{mg}$ and upwards
• D

  Equal and opposite to the resultant of $\mathrm{F}$ and $\mathrm{mg}$

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