True or false, did rainforest kingdoms trade copper, salt, and leather goods for food and crafts from the savannas

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

How have the changes in china's laws affected its economy?

The decision states that legislation cannot overcome social prejudice. can it reinforce social prejudice? how?