D. 1.25 m In a pinhole camera, the relationship between image size and object size is given by: \(\frac{\text{Image Size}}{\text{Object Size}} = \frac{v}{u}\) where \( v \) is the camera length. Given \( v = 25 \, \text{cm} = 0.25 \, \text{m} \). The image is one-fifth the object size, so the magnification is: \(\text{Magnification} = \frac{1}{5} = \frac{v}{u}\) Thus, we can rearrange this to find \( u \): \(u = 5v = 5 \times 0.25 = 1.25 \, \text{m}\).