Final answer:
The meaning of the underlined idiom "at the drop of a hat" is a. instantly.
Step-by-step explanation:
The idiom "at the drop of a hat" means to do something instantly or without hesitation. In the given context, when the speaker's grandparents heard about their illness, they promptly came over without any delay. This idiom emphasizes the immediacy and swiftness of their response, highlighting the grandparents' quick and spontaneous reaction to the news of the speaker being sick.
The phrase "at the drop of a hat" has its origins in the practice of signaling the start of a race or an event by dropping a hat. Participants would begin their actions as soon as the hat dropped, without any prior warning. Over time, the idiom evolved to convey the idea of doing something without hesitation or delay. In this narrative, the grandparents' immediate response to the speaker's illness reflects a sense of care and concern, showcasing the depth of their emotional connection and their readiness to provide support in times of need.
In summary, the use of the idiom "at the drop of a hat" in the passage underscores the quick and unhesitant response of the speaker's grandparents, emphasizing their immediate action upon learning about the speaker's sickness.(Option A)