Read and choose the option with the regular verb in the imperfect tense.

Ok, we must choose the option where the conjugation is in the imperfect tense.
Now, is easy to see that the only option where the verb is conjugated in the preterite tense (usually this conjugation ends in -ía) is option B:
Las Hadas leían hechizos, where the verb is "leer", and when conjugated, it transforms from "le-er" to "Le-ían", so it is also irregular, then this is the correct option.

Because it’s a specified person/thing