What challenges did americans building the panama canal?

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

Who built the first turnpikes in the united states? a) the national government b) state governments c) private companies d) town councils

Which of the following is one way the goverment of russia is considered more limited than the goverment of the soviet union