At the drop of a hat

Do you know the English idiom “at the drop of a hat“? Read the conversation below. Can you guess the meaning?

Nancy: Did Richard help you to move house at the weekend?

Susan: Yes. I called him and he came to help at the drop of a hat.

Does it mean:

a) immediately

b) after dropping a hat

c) after a few hours

d) hesitate

The answer is below! ↓

 

Answer: a) immediately