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'.

[EX Q]: Question: A biosensor consists of: 
 Options:  <1> A receiver, a transducer, and an enzymatic brand. <2> A receptor and an enzymatic brand. <3> A transducer and an enzymatic brand. <4> A receiver and a transducer. <5> A receptor and an antibody.
[EX A]: 4

[EX Q]: Question: If the normal reduction potential of the pair Zn2 + / Zn is -0.76 V: 
 Options:  <1> Aqueous solutions of Zn2 + at pH = 0 release oxygen. <2> Putting metallic Zn in aqueous solution at pH = 0 releases oxygen. <3> Aqueous solutions of Zn2 + at pH = 0 give off hydrogen. <4> By putting metallic Zn in aqueous solution at pH = 0, hydrogen is evolved. <5> Zn2 + dismutates in aqueous solution at pH = 0.
[EX A]: 4

[EX Q]: Question: Among the 5 types of histones of chromatin, the one with the lowest molecular weight is: 
 Options:  <1> H2A. <2> H2B. <3> H1 <4> H4 <5> H3
[EX A]:
4