Let us analyze each pair of terms:
P. Cover - In woven fabrics, the term "cover" refers to the density of the fabric, which is closely related to the concept of "tightness" in knitted fabrics. Thus, P corresponds to Tightness (3) in Group II.
Q. Double-cloth - A double-cloth in woven fabric refers to a fabric where two layers are woven together, and the equivalent term for knitted fabrics is Interlock (1), where two sets of loops are interlocked to create a double-layer fabric.
R. Warp - In weaving, "warp" refers to the set of yarns that run lengthwise, which corresponds to the term Wales (2) in knitted fabrics, as they are the vertical columns of loops in a knitted fabric.
S. Weft - In weaving, the "weft" refers to the yarns that run across the fabric, which corresponds to Courses (4) in knitted fabrics, as they are the horizontal rows of loops.
Thus, the correct matching is P-3, Q-1, R-2, S-4.
Final Answer: \boxed{(B) P-3, Q-1, R-2, S-4}