Why were us troops sent to russia in 1918 during world war 1?

Tori is researching for her blog post about how wearing sunblock can prevent skin cancer, and she finds a page about her topic on the united states centers for disease control website at is this a reliable site for tori’s research? yes, because it is presented by a college or university no, because it is a personal opinion about the subject yes, because it is run by a governmental organization no, because it is intended to advertise a certain product