Final answer:
Gregor's main source of stress is a) his demanding job and family responsibilities, although his transformation leads to loneliness and isolation which worsen his stress.
Step-by-step explanation:
Gregor's present source of stress, aside from his transformation into an insect,a) is primarily his job, demanding family responsibilities, and the fact that his inability to work due to his transformation has likely exacerbated these stresses.
Financial difficulties could also be a concern given his role as the primary breadwinner for the family, but these are not explicitly highlighted as stressors separate from his job and family responsibilities.
Furthermore, Gregor experiences loneliness and isolation due to his condition, which severs the connections he once had with his family and leaves him as an outcast within his own home. Both his job stress and familial obligations, coupled with his isolation, contribute significantly to his stress levels.