This is the most basic construction of the passive sentence. The active equivalent is XはYをVます. Y, the direct object(i.e.,the receiver of the action) of the active construction, is presented as the subject in the passive construction. X is the agent, or someone who performs the action, and Y is the one who receives the action.

Mana was scolded by his teacher.

The teacher scolded Mana.

Note that the passive form is the same as the potential form(Lesson 16-1) for vowel-root verbs(1だんどうし) and 来る(come).

All verbs in the passive form conjugate as vowel-root verb, or 1だんどうし.

The action represented by the verb しょうかいする(introduce) involves three people, therefore two different passive sentences can be formed from the sentence Aさんは Bさんを Cさんに しょうかいしました(Mr./Ms. A introduced Mr./Ms. B to Mr./Ms. C).

I was introduced to Mr./Mrs. C by Mr./Ms. A.

I was introduced to Mr./Ms. B by Mr./Ms. A.