What is the most important duty that an American citizen must perform?

An education expert is researching teaching methods and wishes to interview teachers from a particular school district. she randomly selects ten schools from the district and interviews all of the teachers at the selected schools. which type of sample did she use in this study? a)systematic sample b)probability sample c)stratified sample d)cluster sample

Why should historians question edward ennis? a. they should not. ennis told the truth. b. ennis alerted his superiors to the existence of secret evidence but, when they ignored it, ennis did not make the evidence public. he remained silent. c. ennis made up his secret evidence d. none of the above

Who was the better president between richard nixon and john adams in terms of accomplishments ?