This is a public service announcement about flu prevention.

Two people sharing ear buds on a poster that reads, "Spread Music. Not Flu. Even healthy people can get the flu, and it can be serious. Everyone 6 months and older should get a flu vaccine. This means you. This means protect yourself, and those around you, by getting a flu vaccine."

What is the mood of this public service announcement?

shocking
gentle
serious
upbeat