Correct Answer: energising

Solution : The correct choice is the second option.

Explanation:
Energising is the most appropriate antonym for tiresome, because tiresome refers to something that causes boredom, annoyance, or fatigue. On the other hand, energising implies the opposite effect, suggesting an activity or experience that invigorates, revitalises, and provides energy or enthusiasm.

The meanings of the other options are as follows:

• Exhausting: Extremely tiring or draining, requiring a significant amount of effort and energy.
• Dull: lacking interest or excitement; boring, tedious.
• Boring: not interesting or engaging; causing boredom.