It is dusk and, as I sit upright, I am astonished.

天色已晚，我竟然能坐直起来，使我感到很惊讶。

youdao

While at work, sit upright, with a straight-back, in your chair.

工作时可以坐直，坐在椅子上要挺直腰杆。

youdao

Operator: Let the patient sit upright on bed, but don't get up, and do not panic.

调度员：请让病人半坐床上，不要起来，不要紧张。

youdao

The doctor asked him to sit upright for a while to make sure he felt okay.

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Once it circulated for 10 minutes, I was asked to sit upright inside a circular, open capsule for a Cardiac Computed Tomography (CT) scan.

FORBES: My Visit with a Cardiologist, and What You Should Know About Your Heart

The more traditional method of measuring hearing loss, the distraction test, requires a baby to sit upright on the mother's lap, responding to sound without seeing the source, and therefore cannot be done before 8 months.

BBC: Babies' hearing problems undiagnosed