实际上，是角蛋白使它们变得富有弹性，并且没有角蛋白的话，它们会变得非常坚硬。
In fact, it's keratin which makes them flexible and without it they would be very rigid.
海龟颈部和四肢的肌肉及骨骼的特殊设计使它能把暴露在外的部分缩回去，这样攻击者只能去咬坚硬的外壳。
The particular design of muscles and bones in the neck and limbs of the turtle allow that it can draw in its exposed parts such that an attacker can find nothing but hard shell to bite.
鞋子使人们在坚硬的道路上行走时不会伤到自己的脚。
Shoes keep people from hurting their feet while walking on hard roads.
鞋子使人们在坚硬的道路上行走时不会伤到自己的脚。
Shoes keep people from hurting their feet while walking on hard roads.
应用推荐