Final answer:
OSB and plywood subflooring panels should be installed with the long edge perpendicular to the joists for better load distribution and stability.
Step-by-step explanation:
The correct answer is A. Perpendicular to the joists. OSB and plywood subflooring panels should be installed with the long edge perpendicular to the joists. This is because the joists provide the structural support for the subflooring, and installing the panels perpendicular to the joists allows for better load distribution and stability.
Installing the subflooring panels parallel to the joists (option B) could result in a weaker and less stable subfloor. Installing the panels between the joists (option C) would not provide the necessary support and could lead to sagging or uneven floors. Therefore, the correct installation method is to have the long edge of the panels perpendicular to the joists.