Final answer:
Golfers are vulnerable to lightning strikes when holding a metal club on an open fairway because metal conducts electricity. Sheltering under a tree does not provide safety as trees can attract lightning and convey electricity to nearby objects and people.
Step-by-step explanation:
A golfer carrying a metal club over her shoulder is particularly vulnerable to lightning on an open fairway because metal can act as a conductor for electricity. Being the highest point in an open area increases the risk of attracting a lightning strike. Seeking shelter under a tree, however, would not offer more safety. Trees can also attract lightning due to their height, and if a tree is struck, the electrical current may travel to nearby objects, including people seeking shelter under or near the tree.