This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anatomy
Safety muscle of larynx: 
Select and explain. 
A. Lateral cricoarytenoid, B. Transverse arytenoid, C. Posterior cricoarytenoid, D. Cricothyroids
C: Posterior cricoarytenoid
Answer: C: Posterior cricoarytenoid 
Explanation: During forced inspiration, both pas of the rima are triangular, so that the entire rima is lozenge shaped; the vocal cords are fully abducted and we all know that muscles which open the glottis, are posterior cricoarytenoids. So in one way we can consider them as safety muscles which help in respiration (forced inspiration)