This is a very simple variation that occurs in Part A involving the use of a roll on low G.
The variation can be heard here and is also included in the notation.
Variation 1
Variation 2
This occurs in Part B and to be honest with you I'm not sure if it is actually the standard way of playing it and the that bar it replaces is the variation. In any event the use of the two approaches contrast nicely with each other.
The variation can be heard here and is also included in the notation.