Take a look at the passage again:
To keep the cat from sleeping on her new convertible's canvas top. Kim leaves
the garden hose out. Like a gunslinger in a Western,
she "duels" with Rocky, the family's orange tom, who hisses as vehemently
as the forceful spray of water.
You chose the third part, Like a gunslinger in a Western, she "duels" with Rocky .... This part has a main clause: she is the subject; duels is the verb. A fragment will not have a main clause.
Go back to the passage to try again.