Which of these is a typical speed for a person walking?
0.15 m/s0.15\ \mathrm{m/s}0.15 m/s
15 m/s15\ \mathrm{m/s}15 m/s
1.5 m/s1.5\ \mathrm{m/s}1.5 m/s
150 m/s150\ \mathrm{m/s}150 m/s