Provided by Dow Jones By Sarah McFarlane and Christopher M. Matthews LONDON -- BP PLC returned to profit in the fourth quarter but said the pandemic, which battered the oil-and-gas industry in 2020, would continue to challenge its business this year. Covid-19 has sapped demand for oil, hitting prices, and prompted the world's biggest energy companies to slash spending, cut jobs, write down the value of their assets and -- in the case of BP and Royal Dutch Shell PLC -- lower dividends. The crisis led U.S. oil giants Exxon Mobil Corp. and Chevron Corp. to discuss a merger, according to people familiar with the matter, although the talks didn't progress.