When it asks for preterite, they only want to change the tense of the verb.
The conjugation of conocer / conozco in preterite terms <u>IN YO FORM</u> is
conocí
meaning "I knew"
<h3>Complete the sentence with the correct form of ser: </h3><h3>Tu ________ mi amiga. eres es estás está</h3>
Answer : Tú eres mi amiga.
Explanation : The subject in this sentence is "Tú", that is second singular person, so the verb must be conjugated in the second singular person too. Tú eres.
Hope this helps!