Why do the product of multi-digit numbers with zeros and one-digit numbers sometimes have zero in them and sometimes have no zero in them

Which is the graph of f(x) = (4)x? image for option 1 image for option 2 image for option 3 image for option 4

How do i do this activity, is appreciated

Do some research and find a city that has experienced population growth. determine its population on january 1st of a certain year. write an exponential function to represent the city’s population, y, based on the number of years that pass, x after a period of exponential growth. describe the variables and numbers that you used in your equation.