The ornamental design for a sock, as shown and described.
FIG. 1 is a left side perspective view of a sock of the present invention in a position of use, the right side perspective view being a mirror image thereof;
FIG. 2 is a front view of the sock of FIG. 1 in a flat position; and,
FIG. 3 is a rear view of the sock of FIG. 1 in a flat position.
The solid black portions of the sock shown in the drawings are included for the purpose of illustrating portions of the sock having the color black.
The broken line showing on the bottom heel of the sock in FIG. 3 is for the purpose of illustrating portions of the sock and forms no part of the claim. The broken line showing on the bottom heel of the sock in FIG. 3 is for the purpose of illustrating portions of the sock and forms no part of the claim.