Correct
知根知底
/ zhī gēn zhī de /
Strokes
Example
Definition
know sb's background; know sb thoroughly; have a detailed knowledge of sb
1
Wǒmen
我们
shì
是
lǎopéngyou
老朋友
le
了
,
bǐcǐ
彼此
dōu
都
zhīgēnzhīde
知根知底
。
As old friends, we know each other very well.