You can show that the resistance has changed by reading values of current and voltage from the graph.
Remember that we can calculate resistance (R) by using R = V÷I.
What is the resistance when V=1 and V=3?
Read off values:
R = V÷I = 1÷0.2 = 5 ohm
R = V÷I = 3÷0.4 = 7.5 ohm
The resistance increases!
It's probably wise that you know how to do this!