Correct
乘虚
/ chéngxū /
Strokes
Definition
to take advantage of weakness
Example
As a Verb
take advantage of a weak point in an opponent's defence; act when sb is not vigilant/off guard/not well-defended
1
Chéng
乘
xū
虚
chūjī
出击
attack where the enemy is weak/unguarded; attack when the enemy is undefended