The ornamental designs for a “thermometer”, as shown and described.
FIG. 1 is a perspective view of a thermometer;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The design which is claimed is shown in solid lines in the figures. The broken lines in the figures depict portions of the thermometer that form no part of the claimed design.