Using a relative clause: We have erected barriers between the en

Using a relative clause: We have erected barriers between the environment and ourselves. With every breath we take, we expose our lungs to the outside world, regardless of all the barriers.
【正确答案】：With every breath we take, we expose our lungs to the outside world, regardless of all the barriers which we have erected between the environment and ourselves.
【题目解析】：参考教材P268