Here is what I got as the answer:
Servir —> sirvió
"un tornado". the question is asking <span>This phenomenon rotates violently on its own axis.</span>
Answer:
Present Tense = pienso
Past Tense = pensé
Imperfect Tense = pensaba
Future Tense = pensaré
Conditional Tense = pensaría
Explanation:
You didn't really specify which tense it has to be, but I'm gonna take a guess that you probably want the present tense one.