Ya escribí las cartas. las cartas están

a.

escribidas

b.

escritos

c.

escritas

The correct answer is: c. escritas.

Explanation:

The sentences say: I wrote the letters. Letters are written.

The word "written" is in the participle form, which is a grammatical function that allows a verb to become an adjective in order to manifest a state of the noun. In Spanish it is recognized in the regular verbs by the termination -ado/-ada or -ido/-ida; and in the irregular verbs by the termination -to. Some of the irregular verbs in Spanish are: to break, to open, to write, etc.

As we can see, option a. escribidas is not correct because the termination is -idas is for regular verbs, and we have said that the verb "to write" is not regular in Spanish. Actually, the correct way to conjugate it is with the termination -ito/-ita as options b or c.Now, as the word "letters" ("cartas") in Spanish is a feminine word and for the sake of grammatical coherence, that is really important in Spanish, then it is incorrect to say "Las cartas están escri-tos" for "escritos" is masculine and "cartas" feminine. Therefore, the correct answer is option c. escritas, because is the only one that considers the adequate termination of the participle of the irregular verb "to write" and is the coherent with the feminine gender of the noun.