During Recessions,GDP Falls and Unemployment Increases

During recessions,GDP falls and unemployment increases.Why might the actual output produced not fall as much as officially measured GDP during recessions?

A) There is an increase in involuntary part-time employment during recessions,the output from which is not accounted for in GDP
B) Workers who became unemployed during the recession may produce goods in the underground economy
C) Unemployment benefits to laid off workers are included in GDP
D) Laid off workers may start their own businesses,but profit income from self-employment is not accounted for in GDP
E) Unemployed workers have more leisure time to enjoy.