If nonrenewable energy resources are used to power a light, then the wind energy will be the most efficient. A student created the hypothesis for his experiment. Identify the independent variable.

Which source would best a historian understand the effect of the great chicago fire on families? a. a biography of a chicago family displaced by the fire b. a letter from a grandmother in new york to her family in chicago c. a newspaper editorial about families who were displaced d. an oral history dictated by an adolescent who fled the fire