How did surplus food contribute to the rise of society

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

When and why were fingerprints first used in the united states

Which best describes california population when it became a state in 1850? a.because of the gold rush attracting settlers all over the world california population diverse.bcalifornia had banned foreign immigrants at the start of the gold rush.so,the states population was made up of entirely of americans from other parts of the country.c california had a large african population because many southern planters had moved their enslaved africans to start large farms.d the indian removal act had led to the relocation of thousands of eastern native americans to california.as,a result the majority of californias population was native american