The correct answer is A. Press and hold the shift key while dragging a corner sizing handle.
When you resize an object by dragging a corner sizing handle, the object will maintain its aspect ratio (height and width ratio) if you press and hold the Shift key. This is because the Shift key constrains the movement of the mouse cursor to the horizontal and vertical axes, preventing the object from being stretched or squashed.
Option B is incorrect because pressing and holding the Alt + Ctrl keys while dragging a middle handle will rotate the object around its center point.
Option C is incorrect because dragging a middle handle will only resize the object horizontally or vertically, depending on which handle you drag.
Option D is incorrect because only option A is correct.