Correct Option (A)
The passage explicitly states, "a horrible idea occurred to me." The adjective "horrible" directly conveys a sense of distress or extreme unpleasantness experienced by the narrator regarding the potential oversight of packing the toothbrush. Therefore, "unpleasant" accurately reflects the narrator's immediate emotional state.
Incorrect Options:
Option (B) "sad": While the situation causes distress, "sad" implies sorrow or grief, which does not align with the narrator's expressed feeling of anxiety or panic over forgetting an item. The emotion is more akin to vexation or apprehension rather than sadness.
Option (C) "fantastic": This option is contrary to the tone established by the narrator. "Fantastic" suggests something excellent or wonderful, which is the opposite of the "horrible idea" described in the text.
Option (D) "amusing": Although the situation might be perceived as humorous by a reader due to its exaggerated nature, the narrator's own experience is clearly not one of amusement. The text uses words such as "horrible," "haunts," and "makes my life a misery" to describe the impact of this recurring issue, indicating a deeply bothersome and distressing feeling for the narrator, not an amusing one.