Option C – –30 cm and +30 cm from lens
When image size equals object size for a convex lens (f = 15 cm), the object must be placed at 2F₁, i.e., –30 cm, and the image forms at 2F₂, i.e., +30 cm from the lens.
From Table 9.4 (Chapter 9): when object is placed at 2F₁, the image forms at 2F₂ and is of the same size, real and inverted. Since f = 15 cm, 2f = 30 cm. Using sign convention, object distance = –30 cm (left side) and image distance = +30 cm (right side). Option D is wrong because +30 and –30 would place both on the same side, which is incorrect for a real image.