1. Key idea from the figure

   For two convex lenses, a very common configuration shown in such questions is:

   • rays become parallel after the first lens or before the second lens,
   • meaning the image formed by the first lens lies at the first focal point of the second lens.

   In that case, the separation between the two lenses equals the sum of their focal lengths.

2. Given focal lengths

   $f_1 = 10\ \text{cm}, \qquad f_2 = 15\ \text{cm}$

3. Condition for the figure

   If the image formed by $L_1$ acts as the object at the focal point of $L_2$, then the distance between lenses is

   $d = f_1 + f_2$

4. Calculation

   $d = 10 + 15 = 25\ \text{cm}$

5. Option check

   • A: $25\ \text{cm}$ ✅
   • B: $35\ \text{cm}$
   • C: $10\ \text{cm}$
   • D: $15\ \text{cm}$

Therefore, the correct answer is A.