[单选题]
The variation of ternb)nu 0m*zb,pminpkfxo8do.*97 uk4/yrn+ ech da oa4,lal potential difference$V$ across an electric cell with current $I$ coming out of the cell is shown in the graph.
What are the values of the emf $ϵ$ and internal resistance $r$ of the electric cell used in this circuit?
A. $ϵ =9V$; $r=2.0Ω$
B. $ϵ=8V$; $r=0.5Ω$
C. $ϵ =8V$; $r=2.0Ω$
D. $ϵ=9V$; $r=0.5Ω$