Detailed Instructions: 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'.
Q: Question: What are, among others, the main biases associated with the observer in the framework of observation techniques ?:
Options: <1> The duration of the experiment. <2> The excess of information. <3> The technical accuracy <4> The illusion of learning. <5> The expectation and mechanical errors of registration.
A:
5