1) Look at the graph. What is the independent variable and the dependent variable?

Answer:
Independent Variable = Years
Dependent Variable = Number of Mobiles phone owners
Explanation:
Independent variables are plotted on x-axis and the dependent variables are plotted on y-axis.
In given graph the "Years" belong to x-axis hence, years are the independent variables.
Also, "Number of Mobile phones owners" belong to y-axis hence, this number is the dependent variable.