It was an arduous task for me.

Answer: Option A

Arduous : involving or requiring strenuous effort; difficult and tiring.
Easy : achieved without great effort; presenting few difficulties.
Consuming : (of a feeling) completely filling one's mind and attention; absorbing.
Quick : moving fast or doing something in a short time.
Difficult : needing much effort or skill to accomplish, deal with, or understand.

Antonym of Arduous is Easy