Final answer:
A passage in the novel detailing Gordon Sterrett's self-consciousness about his appearance is the best evidence to support the statement that he is embarrassed by his looks since it directly relates to his internal perception and feelings. Option a is correct.
Step-by-step explanation:
The piece of evidence that best supports the statement that "Gordon Sterrett is embarrassed by his appearance" would be a passage in the novel describing Gordon's self-consciousness about his appearance. This option directly relates to Gordon's emotions and his internal perception of himself, which is where embarrassment originates.
Option b, a character's dialogue expressing concern about Gordon's appearance, provides an external viewpoint on Gordon's appearance, which might indicate that there is something noticeable about his appearance but not necessarily that he is embarrassed by it.
Option c, a detailed analysis of Gordon's physical attributes in the text, simply gives a description and doesn't inherently convey Gordon's feelings about those attributes. Hence, this option doesn't support the idea that he is embarrassed.
Finally, option d, a poem unrelated to Gordon's appearance, wouldn't be relevant in supporting the statement about Gordon's embarrassment regarding his appearance.