与已经下定决心的人争论是毫无意义的。

It would be ___pointless to argue with someone who has already made up their mind.

参与毫无意义的争论只会浪费时间和精力。

Engaging in ___pointless arguments only wastes time and energy.

她意识到向无响应的地址发送电子邮件是毫无意义的。

She realized that sending emails to an unresponsive address was ___pointless.