Correct

根由

/ gēnyóu / 
Strokes

Definition

the whys and the wherefores/the detailed story/root cause

Example

As a Noun

origin; cause; root

1
Gāo
高
fànzuìlǜ
犯罪率
de
的
gēn
根
yóu
由
shì
是
shīyè
失业
hé
和
pínkùn
贫困
  
。

The high crime rate has its roots in unemployment and poverty.

2
Wèntí
问题
de
的
gēnyóu
根由

root of a problem

3
Zhuīwèn
追问
gēn
根
yóu
由

probe into the cause of sth; make detailed enquiries about the cause of sth

4
Zhǎodào
找到
gēnyóu
根由

get to the root (of sth)