How does a guy know when a girl has been sexually active?

(Mustn't tell horrible jokes from high school, mustn't tell horrible jokes from high school...)
If she tells him. There's no sure-fire way for a guy to know a girl has been sexually active ... for example, the hymen may be broken, absent, or unnoticeable for reasons unrelated to sexual activity.
(Mustn't tell horrible jokes from high school, mustn't tell horrible jokes from high school...)
If she tells him. There's no sure-fire way for a guy to know a girl has been sexually active ... for example, the hymen may be broken, absent, or unnoticeable for reasons unrelated to sexual activity.