Fill in the blank with the most appropriate word.
A verb is used to express an occurrence, action, or state. It is the grammatical centre of the predicate in a sentence.
An auxiliary verb is a verb which gives is used in the formation of tenses, moods, tones, etc.
Option C is correct as the sentence is in the simple present tense in the passive form. Therefore, we need to use the past participle here.
The other options are wrong as no other tense can be used here.
The correct answer is C) written