The consequences could be serious.

后果可能是严重的。

《牛津词典》

Be serious for a moment; this is important.

严肃点儿，这件事很重要。

《牛津词典》

She asked me to be serious – said it put her off if I laughed.

她要我严肃一点–说如果我大笑会让她分心。

《柯林斯英汉双解大词典》

Usually, a person is clowning around if he is being funny when he should be serious.

VOA: special.2009.01.11

No, you can't be serious. Really? What?

你开玩笑的吧，是吧？

耶鲁公开课 - 公正课程节选

No, you can't be serious. Really?

你开玩笑的吧，是吧？

耶鲁公开课 - 公正课程节选

There can be serious consequences if the wrong amount or composition of IV fluids is prescribed.

BBC: drip bag

He said he heard a pop in his leg and fears the injury may be serious.

WSJ: Marlins beat Mets 4-3 in 15 innings

But there can be serious side effects, including liver problems and cartilage and tendon abnormalities.

FORBES: Day of Reckoning