Final answer:
Stolid means having or revealing little emotion or sensibility, indicating a character's impassiveness or indifference to emotional responses. option D is correct.
Step-by-step explanation:
In the provided context, the word stolid means having or revealing little emotion or sensibility. Looking at the excerpts given, characters described in such a way often exhibit a lack of emotional response, whether due to philosophical beliefs, as with the Stoics, or due to a neural or psychological state.
The word stolid suggests a kind of impassiveness or indifference to emotion or pain, which can be either due to repression, strength, or perhaps a focus on duty or rationality over emotional expression.