What is the meaning of "reprisal" in paragraph 4

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.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