On the passing ______ of his grandfather, I sent him a bouquet of flowers and a condolence card.

Away

The correct answer is Option (4) → Away

Correct answer: Away

Correct sentence:
On the passing away of his grandfather, I sent him a bouquet of flowers and a condolence card.

Explanation:
The correct phrase is “passing away”, which means death in a polite or gentle manner.

Other options do not form a meaningful or standard expression:

• Passing over → to ignore

• Passing into → incorrect

• Passing by → to move past something

Therefore, the correct option is Away.