Aresearcher conducted an experiment to study the causes of aggression in children. half the children ate a sugared cereal; the remaining half ate cornflakes. the researcher then recorded the number of aggressive acts displayed by the children in a one-hour play period after breakfast. in this experiment:

In this experiment "the type of cereal is the independent variable, and the number of aggressive responses is the dependent variable."
There are two types of variables, dependent and independent variable. The dependent variable is 'dependent' on the independent variable. A dependent variable is the one which is being measured in any experiment and independent variable is the one which is changed in that experiment to examine the consequences for the dependent variable.

The correct answer is a. when they started making tools that will them in cultivating lands, they could raise crops and that made them attached to one place for a longer period of time. after that, they started domesticating animals and building their own permanent settlements that resemble the ones we have today.