Title: Race and ethnicity in the United States Census.
Question: How many races were people asked to mark on the US Census after OMB revised their standards in 1997?

Title: Zinc.
Question: How many people are affected by zinc deficiency?

Title: Immunology.
Question: Immunology studies how which three areas impact one another?

Title: States of Germany.
Question:
In what year did Baden, Württemberg-Baden, and Württemberg-Hohenzollern merge?