Inside one Kyiv neighborhood as it braved the harshest conditions since World War II.

© Finbarr O'Reilly for The New York Times

The U.S. and other exporters are poised for a windfall, but disruptions to Persian Gulf supplies are also pushing gas-buying countries to consider alternatives like coal, solar and nuclear energy.

Sites in China are selling test questions, and online forums offer software that can bypass test protections, according to tutors and testing experts raising alarms.