The correct answer is C. skew(x-angle,y-angle).
A skew transformation is a 2D transformation that causes an object to be stretched along one axis and compressed along the other. The amount of skew is specified by two angles, one for the X-axis and one for the Y-axis.
The skewX(angle) property only specifies a skew along the X-axis, while the skewY(angle) property only specifies a skew along the Y-axis. Therefore, neither of these properties can be used to define a 2D skew transformation along the X- and the Y-axis.
The skew(x-angle,y-angle) property, on the other hand, can be used to define a 2D skew transformation along the X- and the Y-axis. This is because it specifies both the X-axis skew angle and the Y-axis skew angle.
For example, the following code will skew an image by 10 degrees along the X-axis and 20 degrees along the Y-axis:
image.transform = "skew(10,20)";