During a photography class, students are asked to calculate the distance at which a camera lens with a focal length of 50 mm should be placed from a subject to produce an image that is twice the size of the subject. If discrepancies arise in the students' calculations, provide a rationale for the differing results.

• A. At 45 mm and 55 mm from the lens, the image is twice the subject's size but it is in different orientations.
• B. At 45 mm and 55 mm from the lens, the image is twice the subject's size but one is for a single lens and the other is for a combined lens.
• C. At 75 mm and 25 mm from the lens, the image is twice the subject's size but one is a real image and the other is a virtual image.
• D. At 75 mm and 25 mm from the lens, the image is twice the subject's size but the lens is in different orientations.