The ornamental design for a sock, as shown and described.
1. Sock
1.1 : Front
1.2 : Back
1.3 : Left
1.4 : Right
1.5 : Top
1.6 : Bottom
1.7 : Enlarged
The subject article is a sock having a heel portion that is provided with gore lines; the sock is designed to fit the back of the heel at the higher position when it is worn; the white-marked parts are not coming into the scope of the industrial design (disclaimer).