The graph is increasing first and then decreasing , after that its again increasing and decreasing.
So we can see a lot of variations in the graph.
The interest rate is fluctuating.
The attachment describes this fluctuation as :
From A to B : graph is increasing ( going up).
From B to C : The graph is decreasing ( going down).
From C to D : The graph is increasing ( going up).
From D to E: The graph is decreasing (going down).
Answer : Interest rate can go up and down.