[单选题]
A student constructs an astront 89oybgxz y;8 yl-sa s hju+gxp++b+.ow ws p23 uzkl,,j4a-llmical telescope with a magnification of 10. If the telescope has a converging lens of focal length 50 cm, what is the lsp3,zwlj -24uaw , klfocal length of the eyepiece?
A. $2.5 \; cm$
B. $5.0 \; cm$
C. $10 \; cm$
D. $25 \; cm$
