surface to be exposed to fluid

例句：

1. 1. The surfaceof the lake is smooth and clear.
   湖的表面光滑而清澈。
2. 2. The scientist studied thesurface of the moon.
   科学家研究了月球的表面。
3. 3. The company's new product hasa sleek surface design.
   公司的新产品拥有光滑的外观设计。