The correct option is D winter during morning time
The Great Smog of '52 was a severe air-pollution event that affected London during December 1952. A period of cold weather, combined with an anticyclone and windless conditions, collected airborne pollutants mostly from the use of coal to form a thick layer of smog over the city. It lasted from Friday 5 to Tuesday 9 December 1952 and then dispersed quickly after a change of weather.