[单选题]
A student constructsj,27s8vm9 wc)c4enmubs-i f a an astronomical telescope with 4srj b+yesy3 ,3p;wpz a magnification of 10. If the telescope has a converging lens of focal length 50 cm, what is the focal lengtp;pw,3s3jry bs4eyz+ h of the eyepiece?
A. $2.5 \; cm$
B. $5.0 \; cm$
C. $10 \; cm$
D. $25 \; cm$
