Final answer:
Scarlett is upset, but none of the reasons listed—a) argument, b) spilled drink, c) unwanted guest, d) dog getting loose—directly match the provided context. Scarlett's distress is hinted to stem from personal, emotional issues rather than Toby's specific actions.
Step-by-step explanation:
Based on the information provided, Scarlett is upset while Toby is at her house, but none of the specific reasons listed in the options are directly confirmed. However, through the context given, it is evident that Dexter feels uneasiness and concern due to Scarlett's mood during dinner and her later wish to weep, indicating some level of distress. Nevertheless, without a direct link to Toby's actions, we cannot conclude that the reasons a) through d) are correct. Therefore, it seems that Scarlett's upset state may not be directly attributable to Toby's actions, such as an argument, a spilled drink, an unwanted guest, or a pet being loose.
Instead, the source of Scarlett's disenchantment seems to be an internal emotional struggle, as hinted by Dexter's observations of her smiles lacking genuine happiness and her wish to express sorrow in private. This implies that Scarlett may be dealing with personal issues or feelings that are not explicitly mentioned or caused by Toby's presence.