"Most users rarely tweet, but the most prolific 10% create 80% of tweets from adult U.S. users" - this, based on a 2019 study, among a selected nationally representative sample of 2,791 U.S. adults who have a Twitter account and agreed to allow researchers to access that account. This is O a completely randomized experiment O anecdotal evidence a case-control study O a voluntary sample O a matched pairs experiment O a cross-sectional survey O a longitudinal cohort