1. **State the problem:** We need to determine if triangle $\Delta ABC$ with sides $AB=10$, $AC=18.75$, and $BC=28.25$ is a right triangle. 2. **Recall the Pythagorean theorem:** For a triangle to be right-angled, the square of the longest side (hypotenuse) must equal the sum of the squares of the other two sides. 3. **Identify the longest side:** Here, $BC=28.25$ is the longest side. 4. **Calculate squares:** $$10^2 = 100$$ $$18.75^2 = 351.5625$$ $$28.25^2 = 798.0625$$ 5. **Sum of squares of shorter sides:** $$100 + 351.5625 = 451.5625$$ 6. **Compare with square of longest side:** $$451.5625 \neq 798.0625$$ 7. **Conclusion:** Since $10^2 + 18.75^2 \neq 28.25^2$, $\Delta ABC$ is not a right triangle. **Final answer:** Option D. No, because $10^2 + 18.75^2 \neq 28.25^2$.