The underlying cause is not fully understood.

根本原因目前尚未完全清楚。

youdao

Treating the underlying cause is key to reducing the pain.

治疗内在病因对缓解疼痛很重要。

youdao

First, you will need to identify his motivations because unless the underlying cause is addressed he is likely to do it again.

首先，你需要明确他的动机，因为如果深层原因不能解决，他就有可能重犯。

youdao

But the underlying cause is the end of the cold war the foundation of the special relationship for half a century.

ECONOMIST: British anti-Americanism is a muddle not a menace

Well the underlying cause of this mess is the same as it was in the banking crash and Great Recession of 2007-9 - which is the recycling of the great surpluses of the exporting nations, China, Germany and Japan, into the unsustainable debts of the great consuming nations, the US, UK, and much of the eurozone.

BBC: How to catch a falling knife

But the underlying cause of the latest violence is the disenchantment of mostly jobless young people after two decades of street battles, bandhs, and curfews.

ECONOMIST: A new round of anti-government unrest