[单选题]
An object is 15 mm in front of a converging lens, and wsd az1f56o;dvg;9x, xlqcqyn .-rt;the image is 4s:q7zwg ki 5nmg a(g:j(i7nd5.0 mm behind the lens. What is the 7ndmg5wgzs:: ga7i qni5j(k ( focal length of the lens?
A. $11 \; mm$
B. $5.5 \; mm$
C. $3.8 \; mm$
D. $3.2 \; mm$
