[单选题]
An object is 15 mm in front of a convergaozo84p (us n+2m 2n -bqaldo3ing lens, and the image is 4.0 mm behina3-rdg zq8h(,d :g 2cyq fubp o:9ahw5p3 6kwud the lens. What is the focal length of 2 pdk3czrphb9au3hw 65qd:gqwg ,f (y 8oa-u:the lens?
A. $11 \; mm$
B. $5.5 \; mm$
C. $3.8 \; mm$
D. $3.2 \; mm$
