[单选题]
A compound microscope has s 0uvlpcj795ia 1e.;n - ml6b+uvaq0saw8-cm barrel and an objective with a focal length of 8.0 mm. What is the focal length of the eyepiece to giva svn;wmleu b6.0 -+aqe a total magnification of 240?
A. $0.13 \; cm$
B. $1.5 \; cm$
C. $1.9 \; cm$
D. $2.3 \; cm$
