I am very confused plz help

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

Prices for products became more affordable as a result of new forms of ,witch got things to market faster and cheaper

The array of significant individuals who serve as sources of social support is called the social