Final answer:
Structural Light Framing is the softwood lumber grading category that encompasses light farming, stud, structural light framing, and structural joists and plank, indicating the quality and strength required for construction.
Step-by-step explanation:
The softwood lumber grading category that includes light farming, stud, structural light framing, and structural joists and plank is known as Structural Light Framing. This category is utilized by the construction industry to designate the quality and strength of lumber used for framing and structural purposes. For instance, lumber that falls under "stud" grade is typically used for the vertical elements within walls, while "structural light framing" and "structural joists and plank" are designated for load-bearing elements and horizontal spans, respectively. These grades ensure the lumber has met specific criteria for strength and utility in construction.