Explanation:

- In the sentence, "The bereaved mother proudly received the gallantry award __________ her brave son who had laid down his life in the recent war," the focus is on accepting an award relating to her son's heroic actions.

- Option 1: in the name of - suggests doing something as a tribute or honor. While close, it’s not as directly applicable here as "on behalf of."

- Option 2: in lieu of - means instead of or replacing something, which doesn’t fit the context of receiving an award in memory.

- Option 3: on behalf of - indicates representing someone, which is appropriate when accepting an award for a deceased relative. Correct Answer

- Option 4: for the sake of - implies doing something for someone's benefit, which doesn’t directly match the context of an award.