(15 points)the graph below shows lisa's distance from her home (y), in miles, after a certain amount of time (x), in minutes:

four students described lisa's motion, as shown in the table below:

student description
greg she drives at a variable speed for 2 minutes, then stops at a crossing for 2 minutes, and finally drives at a constant speed for the next 4 minutes.
sam she drives at a variable speed for 2 minutes, then stops at a crossing for 4 minutes, and finally drives at a constant speed for the next 8 minutes.
jane she drives at a variable speed for 2 minutes, then drives at a constant speed for the next 2 minutes, and finally drives at a variable speed for the next 4 minutes.
pam she drives at a variable speed for 2 minutes, then drives at a constant speed for 4 minutes, and finally drives at a variable speed for the next 8 minutes.

which student most accurately described lisa's motion?
greg
sam
jane
pam