The power of a system of two thin lenses which share a common axis and are separated by a distance $d$ is given by $P=P_1+P_2-$ $P_1 P_2 d$. Consider two thin lenses with focal lengths $f_1=30.0$ cm and $f_2=40.0 \mathrm{~cm}$. There is an object in front of the first lens at a distance $x \gt f_1$. A real image is created on the screen behind the second lens. If the image on the screen is of the same size regardless of the position of the object, the distance $(\mathrm{in} \mathrm{cm})$ between the lenses is

• A

  $10.0$
• B

  $35.0$
• Correct answer
  C

  $70.0$
• D

  $17.5$

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