英语语法分析

Because they were bipedal, their arms were free to evolve flapping flight, which cannot be said for other reptiles of their time.

因为它们是两足动物，它们的手臂可以自由地进化出拍打的翅膀，这在当时的爬行动物中是不可能的。

Moreover, even though humans have been upright for millions of years, our feet and back continue to struggle with bipedal posture and cannot easily withstand repeated strain imposed by oversize limbs.

此外，尽管人类直立行走已经有数百万年的历史，我们的脚和背部仍在两足行走的姿势中艰难斗争，无法轻易承受过长的四肢持续施加的压力。

This is a robotic walking machine, bipedal, about 4 meters tall.

这是一个行走机器人，双足，高约4米。