oil drop

例句：

1. 1. The oil drop onthe surface of the water was so tinythat it could barely be seen.
   水面上的油滴太小了，几乎看不见。
2. 2. Theoil droplet fell into the glass,leaving a small puddle.
   油滴落入玻璃杯中，形成了一个小水洼。
3. 3.The oil droplet was so small thatit could barely be seen through the microscope.
   通过显微镜观察，这个油滴太小了，几乎无法看见。