Complaining is usually most effective when it is done politely but firmly, and especially when the consumer can demonstrate what is wrong with the item in question.

投诉时语气礼貌且态度坚决通常是最有效的，尤其是当消费者能说明这个物品哪里出了问题时，更加如此。

youdao

Answered the minister, encountering his eye, fearfully, but firmly.

牧师畏惧而坚定地对着他的目光，回答说。

youdao

He strode into my life during that season and set me gently but firmly on a new path.

他在那个时段进入我的生活，让我重新踏上一条新的道路。

youdao

but star Sam Worthington says the exploits of Perseus are firmly rooted in the ancient tales of mythological heroes.

VOA: standard.2010.04.08

We have no other choice but to go forward and to keep our minds on acting firmly on the knowledge we already have;

VOA: standard.2010.05.17

We should politely but firmly resist those who tell us this is not our business.

WSJ: Confronting Gadhafi Is Not Enough

That was a largely symbolic move, but firmly drew the line between Old and New Labour.

BBC: David Cameron

If anyone commits a criminal offence they will be dealt with fairly but firmly.

BBC: Police warning ahead of EDL protest in Blackburn