A. reservada
The person is saying that they don't like to spend time with their friends or speak on the phone. They are reserved. Soy in english would translate into "I am". Only when speaking about character traits or permanent things such as "I am tall" "I am kind" etc.
Conjugations of verbs for the formal "you" in Spanish are the same as for the subjects el and ella; in present tense, they usually end in -a.
The option you have checked is in past tense ("I bought this"); the present tense conjugation is compra.
Usted compra esto.
Again, the conjugation of verbs for the formal "you" in present tense almost always end in the letter "a"; the correct conjugation is estudia.
Usted estudia <span>matemáticas.</span>
