讲解：
catch sb doing
当场发现(或发觉):
I caught her smoking in the bathroom.
我撞见她在盥洗室里抽烟。

erase sth (from sth)
清除；消除；消灭:
She tried to erase the memory of that evening.
她试图忘却那天晚上的事。

have a noun tongue
说话方式:
He has a sharp tongue.
他说话尖酸刻薄。

target (at)sb
面向,把…对准(某群体):
The campaign is clearly targeted at the young.
这个宣传计划显然是针对青年人的。

on purpose
故意；有意地:
He did it on purpose, knowing it would annoy her.
他明知会激怒她,却故意那么做。