step vein

例句：

1. 1. The doctor advised him to step back from the edge of the pool and take a deep breath.
   医生建议他从池边退后并深呼吸。
2. 2.She stepped into the room with a smile on her face.
   她带着微笑走进房间。
3. 3. The scientist studied the structure of the human brain by examining the steps of its veins.
   科学家通过观察人脑的血管结构研究大脑的结构。