Which function is graphed below?

On a coordinate plane, an exponential decay function is shown. The curve starts in quadrant 2 and decreases into quadrant 1. It crosses the y-axis at (0, 3) and approaches y = 0 in quadrant 1.
y = one-third (3) Superscript x
y = 3 (one-third) Superscript x
y = (one-half) Superscript x Baseline + 2
y = (2) Superscript x Baseline minus 1