英语语法分析

Hold the floss tightly between your thumbs and forefingers, with about an inch (2.5 cm) of floss between them.

两只手的食指和大拇指分别捏紧牙线的一端， 中间留出一英寸长（2.5厘米） 。

The old man tapped the steering wheel once with his foreFingers.

那位老爷子用食指轻轻拍着方向盘。

Use the thumbs and forefingers to guide the floss between the teeth.

握紧牙线，用食指和拇指轻柔地在牙缝间操作牙线。