What is the most logical next event?

A university swim team is doing a fund raiser washing cars. A member explains what they are doing. a man on the street with a poster sign

Available options:
[I] at his face grabs a bottle and scrubs the cars.;
[II] ons his arm creates a big splash.;
[III] on his neck explains again.;
[IV] tries to get customers.;
[IV]