What material replaced stone as the primary materials used to make tools and machines by humans

Which of the following methods could be considered a “best practice” in terms of informing respondents how their answers to an on-line survey about personal information will be protected? respondents are informed that investigators will try to keep their participation confidential; however, confidentiality cannot be assured. respondents are informed that a research assistant will transfer all the research data to a password-protected computer that is not connected to the internet, via a usb flashdrive. the computer is located in a research team member’s office. the investigator uses the informed consent process to explain her institution’s method for guaranteeing absolute confidentiality of research data. the investigator uses the informed consent process to explain how respondent data will be transmitted from the website to his encrypted database without ever recording respondents’ ip addresses, but explains that on the internet confidentiality cannot be absolutely guaranteed.

Aisha has finished working on a word processing document that contains 15 pages. she has added some special elements in the first three pages, page 9 and 10, and page 15 from the document. she wants to print only these pages to see how they look. which option is the correct way to represent (in the print dialog box) the pages that aisha wants to print

Which of these is most responsible for differences between the twentieth century to the twenty-first century?