the respiratory tract clogged

If the subject is closed, the respiratory tract may become clogged due to reasons such as the backward slippage of the tongue or the escape of foreign bodies through the respiratory tract. In this case, if there is no trauma to the spine, the position of - - - - is given to open the airway.

Which is left blank in the above explanation?

1- shock

2- sitting

3- half-prone-side

4- head back-chin up

The right answer is:  4- head back-chin up