question: sampling survey:sampling principle
choices.label: A B C D
choices.text: questionnaire:asking for advice equipment operation:operating procedures mathematical models:modeling software person interviews:interview contents
explanation: "sampling survey" must follow the "sampling principle". the "questionnaire" does not have to "ask for advice". "equipment operation" must follow the "operating procedures". "modeling software" is a tool for "mathematical models". the "person interview" does not have to follow the "interview content".
relation: sampling survey sampling principle R3.10
relation: equipment operation operating procedures R3.10
relation: mathematical models modeling software R3.8