Which grade of plywood contains some blemishes and an occasional small knothole?

Grade C plywood is characterized by its moderate appearance and structural integrity, making it suitable for applications where visual quality is not as critical. This grade can include some blemishes and an occasional small knothole. The presence of these imperfections indicates that it is not suitable for high-visibility projects but can still provide adequate strength and functionality for various uses, such as in construction or utility sheathing.

In contrast, Grade A plywood is typically free of blemishes and defects, making it ideal for high-quality finishes. Grade B plywood may have a limited number of small knots but maintains a higher visual standard than Grade C. Grade D plywood shows more imperfections and is largely used for rough construction, where appearance is not a priority. Thus, Grade C's allowance for a few blemishes and small knots aligns perfectly with the characteristics described in the question.