Your back should remain straight and upright at all times.

你回直，并应保持直立在任何时候。

youdao

I had to sit on my stool with back straight and upright, correctly holding the brush, so I loved making random drawings.

而我却得挺着腰、直着背、握着笔、坐在小板凳上，所以我还是喜欢乱画。

youdao

Perhaps the crooked tree is no beautiful than the straight and upright tree, but the latter is interested and felled by carpenter.

歪斜的树也许不如挺直的树好看，但是挺直的树被木匠相中而砍伐。

youdao

Anderson and Bresnan have been in Twenty20 mode and used to bowling more variety with slow balls and off-cutters - they haven't been bowling seam upright with straight wrists.

BBC: Jonathan Agnew column