>> o'donnell: good evening to our viewers in the west, and thank you for joining us. we're going to begin tonight with new signs and worries that the covid pandemic is once agan tightening its grip. the stock market had its worst day in months on fears that a mid-summer surge driven by the highly contagious delta variant could bring another global economic slowdown. the dow dropped more than 2% with airlines, banks and oil companies taking losses. tonight the other headline, the american academy of pediatrics is recommending all students wear masks this fall. regardless of whether they've had their shots. and tonight the stunning reversal from the white house as president biden walks back his statement that facebook is "killing people." today he said he meant to blame a small number of bad actors on the social media platform, but he is calling on facebook to do more to stop misinformation. and then there's this, a u.s. gymnast tested positive in japan, the first of the u.s. athletes to do so in the olympic