According to Mankiw and the data he provides, which of the following is not true of US life expectancy?

A. Life expectancy at birth more than doubled over the 20th century

B. Overall, the increase in life expectancy was larger in the first half of the 20th century than the second half

C. Improvements in sanitation have been important contributors to rising life expectancy since 1900

D. Improvements in automotive safety have been important contributors to rising life expectancy since 1950