Xinhua/Wang Ying via Getty Images US stock futures fell Wednesday, as markets stayed cautious after a choppy session the previous day. Investors may be concerned that post-pandemic recovery may be less exuberant than expected, an analyst said. Bitcoin continued Tuesday's sell-off after El Salvador became the first country to make it legal currency. Sign up here for our daily newsletter, 10 Things Before the Opening Bell. US stock futures fell sharply Wednesday as investors witnessed a sell-off across multiple asset classes, with markets taking a cautious tone as confidence in the prospects for a strong post-pandemic recovery appeared to falter.Futures linked to the Dow Jones were down 0.5%, while those on the S&P 500 dropped 0.4%, and the Nasdaq lost 0.3% as of 4:20 a.m.