This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Ear, Subject name: ENT
In an alaryngeal speech, with fistula based voice prosthesis, which of these prosthesis has the feature of "Loading tool with an instantaneous opening of the oesophagal flange 
Select and explain. 
A. Blom-Singer Indwelling, B. Provox 2, C. Panje voice button, D. Blom Singer duckbill
B: Provox 2
Answer: B: Provox 2 
Explanation: Alaryngeal speech is a speech made using sources other than the glottis in the larynx to create voiced sound. There are three types: oesophagal, buccal, and pharyngeal speech. In oesophageal tracheoesophageal puncture can be made and utilized Provox2 is a diameter indwelling silicone voice prosthesis that can be inseed, immediately after TE puncture (primary or secondary), without the need for temporary stenting. Ref: https://en.m.wikipedia.org/wiki/Voice_prosthesis