The four parts in which I had to go through this investigation was:
Part 1: Practice
Part 2: Does mass affect the swing rate of a pendulum?
Part 3:Does Arc length affect the swing rate of a pendulum?
Part 4:Does Length affect the swing rate of a pendulum.
It asks why was it necessary to do this investigation in four parts?
I just put, that it was necessary to do this investigation in four parts because each part has a variable which we have to go through to see if it will affect the swing rate of the pendulum.
More info would be appreciated, thanks :-)