When comparing mortality rates across different Chicago neighborhoods, the most likely cause for adjusting or standardizing the rates by median household income in the neighboirhood is: A. The neighborhoods being compared differ in median household income which is also related to mortality. B. Mortality rates vary by gender. C. The neighborhoods median household income is associated with increased environmental hazards. D. The neighborhoods being compared have different age distribution. E. The neighborhoods being compared differ by race and the outcome rates vary by race