[单选题]
How far from a lens of 1-hjj6 tjr4hkfocal a3o4 k 9hak pgjn;;.k5:lipcblength 50 mm must the object be placed if it is to form a virtual image magnified in size by a factor of ;ag;klp ic 3jb .k9n:h5ap o4kthree?
A. $33 \; mm$
B. $42 \; mm$
C. $48 \; mm$
D. $54 \; mm$
