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: Gallium is the element that is under the aluminum in group 13 of the periodic table. Thus: 
 Options:  <1> It burns in oxygen giving Ga2O. <2> It is stable to air due to a protective oxide layer. <3> It dissolves very quickly in nitric acid. <4> It is not soluble in basic water with hydrogen evolution. <5> It has a melting point a little higher than aluminum.

A: 2
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Q: Question: The CD40 ligand molecule (CD40L or CD154) is expressed in: 
 Options:  <1> Virgin T lymphocytes. <2> Activated T lymphocytes <3> NK lymphocytes. <4> Virgin B lymphocytes. <5> B activated lymphocytes.

A: 2
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Q: Question: A group of researchers conducted a prospective study to evaluate the efficacy of three alternatives in the treatment of acute otorrhea in children with tympanostomy tubes. Randomized, 76 children received oral amoxicillin-clavulanic acid, 77 received ear drops with hydrocortisone-bacitracinacolistin and other 77 children did not receive any pharmacological treatment, only observation. The main variable was the presence of otorrhea. What kind of study is it? 
 Options:  <1> Cohort study. <2> Post-authorization study of prospective follow-up. <3> Post-authorization study linked to the authorization. <4> Clinical trial <5> Transversal study.

A:
4
****