Indecent exposure?

A blonde is walking down the street with her blouse open, exposing one of her breasts.

A nearby policeman approaches her and remarks, "Ma'am, are you aware that I could cite you for indecent exposure?"

"Why, officer?" asks the blonde.

"Because your blouse is open and your breast is exposed."

"Oh my goodness," exclaims the blonde,

Spoiler:

"I left my baby on the bus!"