1.It is pronoumced by raising the tongue tip against the upper teethridge to block the air and then putting it down to release the air.

1.下唇和上齿接触，形狭缝，气流狭缝中磨。

2.It is pronounced by raising the tongue tip against the upper teethridge to block the air and then putting it down to release the air.

2.舌尖顶住上齿龈，阴住气流，然后移下舌尖，放气流。