AREA\[=\frac{x\sqrt{4{{y}^{2}}-{{x}^{2}}}}{4}\] II. Perimeter\[=(2y+x)\] III. Height\[=\frac{1}{2}\sqrt{4{{y}^{2}}-{{x}^{2}}}\] \[\therefore \] I, II and III are all TRUE. So, the correct answer is d.