[单选题]
How far from a 50-mm focal length 1pm.asqg0gx )wg1 (xvlens, such as is used i pzkgt0w-f751 4njizo n many 35-mm cameras, must an object be positioned if it is to form az0izpg17t5 ojk -4wfn real image magnified in size by a factor of three?
A. $46 \; mm$
B. $52 \; mm$
C. $58 \; mm$
D. $67 \; mm$
