Definition: In this task, you are given a multiple-choice question about healthcare. Answer the question based on your information and classify your answers into '1', '2', '3', and '4'.
Input: Question: From among the following, indicate the most toxic substance according to the 50 lethal dose value:
Options: <1> Strychnine. <2> Nicotine. <3> Morphine. <4> Botulinum toxin. <5> Curare.
Output:
4