I claim the ornamental design for a sink, as shown and described.
FIG. 1 is a top perspective view of an embodiment of the claimed design;
FIG. 2 is a top plan view of the claimed design of FIG. 1;
FIG. 3 is a front elevation view of the claimed design of FIG. 1;
FIG. 4 is a right-side elevation view of the claimed design of FIG. 1;
FIG. 5 is a left-side elevation view of the claimed design of FIG. 1;
FIG. 6 is a rear elevation view of the claimed design of FIG. 1; and,
FIG. 7 is a bottom plan view of the claimed design of FIG. 1.
The ornamental design which is claimed is shown in solid lines in the drawings. The broken lines in the drawings are for illustrative purposes only and form no part of the claimed design.