A chest physician performs bronchoscopy in the procedure room of the out patient department. To make the instrument safe for use in the next patient waiting outside, the most appropriate method to disinfect the endoscope is by :
2% Glutaraldehyde is knows as cidex (Aldehyde disinfectant) specially effective against tubercle bacilli, fungi and viruses. It is most commonly used for cystoscope, endoscope, bronchoscopes etc., which can’t be disinfected by heat.
Also used to treat corrugated rubber anesthetic tubes and face masks, plastic endotracheal tubes, metal instruments and polythene tubing.

Other choice:

70% alcohol is used as skin antiseptic. It acts by denaturing bacterial proteins.
Methylated ethyl alcohol is MC alcohol used for skin disinfection and hand washing.
2 - 3 percent formaldehyde (20 - 30 ml of 40% formalin in one litre of water) is used for spraying rooms, walls, furnitures and disinfecting blankets, beds and books. It is most effective at high temperature and relative humidity of 80-90%.
Sodium hypochlorite is recommended for sterilizing infant’s feeding bottles. It acts in the same way as bleaching powder and is more strong.
70% alcohol for 5 min
2% glutaraldehyde for 20 min
2% formaldheyde for 10 min
1% sodium hypochlorite for 15 min