Which of the statements $a,b$ and $c$ is true?

Pane is the base class for layout panes. This can be used to position nodes at fixed locations$-$known as absolute positioning.

TilePane A horizontal or vertical grid of equally sized tiles. Nodes that are tiled horizontally wrap at the TilePane's width. Nodes that are tiled vertically wrap at the TilePane's height.

StackPane Places nodes in a stack. Each new node is stacked atop the previous node. You might use this to place text on top of images, for example.

All of these statements are true.