When did valentine's day become a holiday in the united states?

The health care system in is referred to as a singleminus−payer health care system, and is a system in which the government provides national health insurance to all residents.

The platt amendment was a treaty that allowed the united states to build military bases in which country?

Which of the following  bestillustrates a negative reinforcer?               a.  copland gives up candy to stave off chronic acid indigestion.    b.  nancy learns that she prefers chocolate over vanilla.    c.  carmine changes his major to english lit after failing a math exam.    d.  on a hot day, lindberg always drinks lemonade.