到底发生什么事

what exactly happened

→ 到底
phrase Rare #21,404
what exactly happened 到底 adds emphasis and can make the question sound insistent or urgent.
CH: 你到底发生什么事了?
EN: What exactly happened to you?

马赛罗告诉我到底发生什么事了

Marcelo, tell me what happened.

— 甜蜜的生活 (1960)

到底发生什么事?

What on earth happened?

— 隐藏摄像机 (2005)

谁知道到底发生什么事?

Who knows what actually happened?

— 奥本海默 (2023)

你那一天离开之后到底发生什么事?

What exactly happened after you left that day?

— A Sun (2019)

到底发生什么事了?

What on earth happened?

— 辉夜姬物语 (2013)

昨天到底发生什么事?

What exactly happened yesterday?

— A Sun (2019)