Question asked for a gerund but no gerund in answer choices

Question

In a 10-question test these was the question:

¿Por qué lo ________ ?
Why are you cursing him?

I expected the answer would be a gerund, but it was not. Why was "cursing" used and not "curse?" As in, "Why (do) you curse him?"

Accepted Answer

Hola William
In test-questions where the testing is to do with conjugation of a certain verb or group of verbs we always add a hint saying exactly which tense and verb we require. In this case you can see the hint saying: Hint: Use "tú' form for conjugating "maldecir" in El Presente
The translations don't always match exactly as we try to use the most natural translation in English so there is always a balance there. I understand that if you miss the hint and go straight to what the translation says you may answer with the wrong conjugation or verb, this is why it's important to always read the hint. 
Once you read the hint you focus on that specific tense. 
I hope this helps.
Saludos