Since apes walk on all fours, they have long, extremely burly arms.猿行走时四肢并用, 因此前肢很长, 并且极其结实。

She was crawling around on all fours like a dog.她手脚并用, 像狗一样爬来爬去。

We got down on all fours and looked under all the seats.我们趴在地上查看了所有座位下面。