Possible response:

The mother's face looked like that of a corpse in the poem "My Mother at Sixty Six" by Kamala Das because of several factors that the speaker noticed during a car ride with her aging mother. These factors include:

Physical appearance:
- The mother's skin was "grey and speckled" like "palms of old, old women" (lines 4-5).
- Her face was "ashen like that of a corpse" (line 6).
- Her eyes were "closed" or "half-open" and "veiled" (lines 7-8).
- Her hair was "thin" and "grey" and "scarcely covered" her scalp (line 9).

Emotional state:
- The mother seemed "drowsing" or "nodding" and "bored" or "tired" (lines 1-3).
- She did not respond to the speaker's questions or comments, except with a "grunting" sound (line 11).

Contextual clues:
- The speaker was driving her mother to the airport, where the mother would leave for a pilgrimage to "Benares or Allahabad" (lines 12-13).
- The speaker had just returned from a trip abroad and had not seen her mother for some time (line 14).

Overall, the mother's appearance and behavior suggest that she may be experiencing some physical or mental decline due to aging, illness, or exhaustion. The comparison to a corpse also implies a sense of mortality and fragility, as well as a cultural association with death rites and rituals. The speaker's own emotions are mixed between concern for her mother's well-being and a sense of detachment or distance from her, as well as a fear of losing her. The poem thus explores the themes of aging, mortality, filial love, and cultural identity.