What is the best way to check the reliability of a resource

What is zinn's approach to the study of history? what does he suggest occurs when history is told is the story of human progress?

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

What major land feature is located at 0* and 20* e? a sahara desert b kalahara desert c congo basin d the alps