<h2>Right answer: Usted
</h2>
<u>Explanation:</u>
The 2nd person in singular <em>you</em> has two forms of speaking in Spanish (Castilian):
<h2>Tú
</h2>
It is used with friends, with relatives and in <u>informal</u> situations
<h2>Usted
</h2>
It is used with people in<u> formal</u> situations: strangers, with elderly people, with people with a degree, such as Dr. or Dra., teacher, Miss, Mr, Mrs.
Therefore, the answer is A.
The other options are <u>incorrect</u> because:
él (he) is the 3rd person in singular
tú (you) is the informal of the 2nd person in singular (as explained above)
ustedes (you) is the 2nd person in plural
