The correct answer is: D. Right angled triangle
The center of gravity of a plane lamina is the point at which the entire weight of the lamina can be considered to be concentrated. The center of gravity of a plane lamina will not be at its geometrical center if the lamina is not symmetrical. A right angled triangle is not symmetrical, so the center of gravity of a right angled triangle will not be at its geometrical center.
For a circle, equilateral triangle, and rectangle, the center of gravity is at the geometrical center. This is because these shapes are symmetrical. The center of gravity of a symmetrical shape is always at its geometrical center.
Here is a diagram of a right angled triangle with its center of gravity marked:
[Diagram of a right angled triangle with its center of gravity marked]
The center of gravity of a right angled triangle is located at the intersection of the medians. The medians of a triangle are the lines that connect each vertex to the midpoint of the opposite side.
I hope this explanation is helpful! Let me know if you have any other questions.