Detectives are so far at a loss to explain the reason for his death.

至今侦探仍茫然无法解释他的死因。

《牛津词典》

Did you explain the reason for him?

你向他解释原因了吗？

youdao

When these all-too-human mishaps do occur, it is important to explain the reason for being late.

当这些人之常情的不幸意外真的发生时，务必要解释迟到的理由。

youdao

Mr Coppinger is required to explain the reason for the appointment which led to the police authority's chief executive Stuart Pudney's being replaced.

BBC: Barry Coppinger

How does one explain the reason for engaging in unauthorized discretion?

FORBES: Morgan Stanley Broker Cited For Discretion And Unsolicited Trades

Authorities did not explain the reason for the raid, which including agents from the Federal Bureau of Investigation, the U.S. Department of Health and Human Services and the Florida Attorney General's Medicaid fraud unit.

FORBES: Magazine Article