1. Is he serious about leaving the company?
(会社を辞めることは彼は本気なのだろうか?)
2. The boss was serious about the lack of productivity .
(上司は生産性の欠如について真剣に考えている)
3. He has to be serious about his work in order to succeed.
(成功するためには仕事について彼は真剣に考える必要がある)
4. Are they serious about this?
(彼らはこのことについて本気なのだろうか?)
5. I was serious about moving to a different country, but I changed my mind.
(私は他の国へ引っ越すことを真剣に考えていたが、考えが変わった)