The word "copious" means abundant, plentiful, or in a large quantity.
\[ \text{Copious} = \text{Abundant or in large quantity} \]
In the given sentence, "copious drainage from the wound" means that a large amount of fluid was coming out of the wound, requiring immediate medical attention.
Therefore, the option "A lot" correctly conveys the meaning of copious.
Explanation of the other options:
Therefore, the correct answer is: \[ \boxed{\text{Option 3 — A lot}} \]