Answer:
A. After Sam asks the speaker to make him a promise, the speaker says, "[Sam] seemed so low that I couldn't say no."
Step-by-step explanation:
In the poem, the speaker tells about his sojourn with Sam McGee in the freezing cold in Canada. Sam knew he was going to die because the cold was freezing him to the bones. So he made the speaker promise to cremate him since he feared the icy grave.
The speaker sympathized with him when he noted his appearance, which he observed as being so low. He apparently felt pity for him after observing his failing health.