[单选题]
A student constructs an astronomical teleskiu0:p pnpiv (.8aft59b p ztq8.8ylycope with a magnification of 17d2ucswin: v 6 z4d-g 1kkdxm-0. If the telescope has a converdcvk2 w:zks 4nd-d 1-7m xg6uiging lens of focal length 50 cm, what is the focal length of the eyepiece?
A. $2.5 \; cm$
B. $5.0 \; cm$
C. $10 \; cm$
D. $25 \; cm$
