When were the first commercial valentines day cards sold?

"people are the greatest resource that a country has". justify.

1.3.3 quiz: primary and secondary sourcesquestion 4 of 102 pointsa secondary source is reliable and credible if the person who created thesource is an expert on the topic, is educated and respected in the field ofstudy, and:

What kind of geography deals with people and how they affect the world ?