The ornamental design for a crib, as shown and described.
FIG. 1 is an upper perspective view showing my new design for a crib.
FIG. 2 is a lower perspective view thereof.
FIG. 3 is front side plan view thereof, the back side being a mirror image.
FIG. 4 is a right side plan view thereof, the left side being a mirror image.
FIG. 5 is a top side plan view thereof; and,
FIG. 6 is a bottom side plan view thereof.
The broken lines adjacent the shaded areas represent the boundaries of the claimed design, while the other broken lines representing the outline of portions of the crib depict environmental subject matter only, and form no part of the claimed design.