<prompt> Scabbard Trachea; True is?Flattening of tracheaCaused by lateral compression by swellingsCaused by lateral compression by tumorsAll of the above  <response>: SCABBARD SABER-SHEATH TRACHEAFlattening of trachea caused by lateral compression by swellings or tumors.Causes: Carcinoma thyroid, thyroiditis, carcinoma larynx, goitre. 