Final answer:
The word that means 'to annoy, irritate or vex' is 'irk,' which is option A. The other options have different meanings and are not synonymous with annoying or irritating someone.
Thus, the correct option is A.
Step-by-step explanation:
To annoy, irritate, or vex means to cause someone to feel annoyed, irritated, or vexed. The correct option from the given choices is 'A. irk'. When something irks someone, it bothers or annoys them. For example, if a noisy neighbor constantly plays loud music late at night, it can irk the other residents in the building.
Therefore the correct option is A.irk