Final answer:
The correct answer to the question is C) "Ser", as it is the only irregular imperfect verb listed. The other verbs outlined are regular imperfect verbs.
Step-by-step explanation:
The irregular imperfect verb in Spanish (SIV) among the options provided is C) "Ser". Unlike regular verbs in the imperfect tense, which follow a set pattern of conjugations, irregular verbs deviate from these patterns. For instance, the verb "comer" (to eat) is a regular verb in the imperfect tense and follows a predictable pattern (comía, comías, comía, comíamos, comíais, comían), as do "escribir" (to write) and "vivir" (to live). However, "ser" (to be) is conjugated uniquely in the imperfect tense: era, eras, era, éramos, erais, eran. This illustrates why "ser" is the correct answer to being an irregular imperfect verb in Spanish.