Step 1: List Sri Lanka's highest score in each Cup.
From the graph, Sri Lanka scored 280 in Cup A, 320 in Cup B, 300 in Cup C and 315 in Cup D.
Step 2: Find the percentage change from each Cup to the next.
Cup B compared to Cup A: \( \frac{320-280}{280} \times 100 = 14.29\% \) increase.
Cup C compared to Cup B: \( \frac{300-320}{320} \times 100 = -6.25\% \), which is a decrease, not an increase.
Cup D compared to Cup C: \( \frac{315-300}{300} \times 100 = 5\% \) increase.
Step 3: Compare the increases and reject any decrease.
Only Cup B (14.29%) and Cup D (5%) show a genuine increase over the previous Cup.
Cup B gives the higher increase of the two.
Final Answer:
The highest percentage increase in Sri Lanka's score over the previous Cup happens in Cup B. \[ \boxed{\text{Cup B}} \]