[单选题]
How far from a lens of f ( ig* 9bd6;jklqm-qorocal length 50 mm mp,bxhsmp9 j3ipk7 h7( ust the object be placed if it is to form a virtual image magnified in size by a fasbh3(p7kj9, 7 ipmxhp ctor of three?
A. $33 \; mm$
B. $42 \; mm$
C. $48 \; mm$
D. $54 \; mm$
