Final answer:
William Tell takes two arrows from his quiver intending to kill Albrecht Gessler if the first arrow accidentally kills his son in the apple-shooting ordeal.
Step-by-step explanation:
William Tell removed two arrows from his quiver because, according to the legend, the second arrow was for Albrecht Gessler in case he accidentally killed his son with the first arrow. Gessler was the tyrannical official who ordered Tell to shoot the apple from his son's head as a test of his archery skills. Tell reasoned that if his son were to die by his hand, he would also kill Gessler, whom he held responsible for putting them in such a perilous position.