[单选题]
How far from a 50-mm focal length lenv sqj.9kk*uh-5+wua xuupm:3s, such as isrw 0umf9k 1hly5vy sai1kie3(; ar,2w used in many 35-mm cameras, must an object be positioned if it is to form a real image magnified inmhr a2yr11eywia ( 9k3;5k0l ,wf isuv size by a factor of three?
A. $46 \; mm$
B. $52 \; mm$
C. $58 \; mm$
D. $67 \; mm$
