DOHA, Qatar - Qatar's stock exchange dropped Sunday as the tiny Gulf nation braced for a deadline to accept demands from four Arab countries in part over what they allege is its support for extremist groups. Saudi Arabia, the United Arab Emirates, Egypt and Bahrain cut off ties with 2022 FIFA World Cup host Qatar in early June, restricting access to their airspace and ports and sealing Qatar's only land border, which it shares with Saudi Arabia. ...