Mexico city is an example of how humans alter their environment because it was

In which research method does a researcher change the value of one variable to determine how the change affects another variable? a. experiment b. observational research c. survey d. case study

Did the writers of the declaration of independence accomplish their goals (did we get our independence and the new government we wrote about)?

The civilian conservation corps (ccc), an agency established during the great depression as part of the new deal, created jobs for people who were unemployed. what kind of work did people do as part of the ccc? a. built libraries and hospitals b. maintained state and national forests c. photographed migrants and the homeless d. constructed roads and bridges