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'.
Problem:Question: Enzymatic regulation by phosphorylation:
Options: <1> It is reversible. <2> It requires enzymes that directly introduce the Pi. <3> Introduce the Pi into acidic and basic amino acids. <4> Always activate enzymes. <5> It is carried out by phosphatases.
Solution:
1