Having found their yellow ball surrounded by leaves
in a bunker may the player touch those leaves ...
a) ... with their club while preparing to make
b) ... in taking a practice swing?
c) ... on the backswing of their stroke?
a), b) and c) No. Rule 13-4c.
Note: Rule 13-4c states that
before making a stroke at a ball that is in a hazard
the player must not touch or move a loose impediment
lying in or touching the hazard. A stroke only
commences with the forward movement of the club
made with the intention of striking at and moving