[单选题]
The variation of terminal potent:a kif1,w 4s1c(vcjl pial differeay-)8uybsh55)1vld mkb +kw ance$V$ 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. $ϵ=9V$; $r=0.5Ω$