A. This detail establishes that Gregor had another profession before becoming a salesman.
Explanation:
Option A is the correct answer. It actually establishes the author's purpose for including the detail about the protagonist in the text.
From the text, we discover that the author included the description just as he was describing the setting where Gregor was. The author mentioned the wash up breakfast that was on the table, about the hospital and about Gregor's father who was reading newspaper. Then the author mentions the picture that hung on the wall. It was at this point that the information of the photograph informs the reader that Gregor had another profession before becoming a salesman.
