After calculating the box height (Z) in R[2], which instruction would set the Z height of the box in PR[10]?

The instruction that sets the Z height of the box in PR[10] utilizes the appropriate index for the Z-axis coordinate within the PR (Position Register). In the FANUC programming environment, the PR data structure typically consists of several components that correspond to different axes of movement in a Cartesian coordinate system.

In this context, the second index of the PR register corresponds to the Z-axis. Therefore, when you use PR[10;3] = R[2], you are correctly assigning the value stored in the register R[2]—which represents the calculated height of the box—directly to the Z coordinate of position register 10. This correctly reflects the relationship between the register and the Z-axis.

The other options specify different indices which correspond to other axes or values (such as the X or Y coordinates, depending on the specific structure of the PR array). Thus, option B is the only one that accurately sets the Z height using the correct indexing in the context of FANUC programming.