Questions

Epiglottis is that prevents food from entering the windpipe. 

It is a cartilageous flap that flaps opens and closes when swallowing. When you swallow, the epiglottis flattens backward to cover the entrance to your larynx and prevent food from entering the lungs and windpipe. The epiglottis returns to its usual position after swallowing.

Operating system software is that manages resources on a network.

DNA is a double-stranded molecule twisted into a helix. The shape of DNA is a double helix, which is like a twisted ladder. The sides of the ladder are made of alternating sugar and phosphate molecules. Deoxyribose, which is a pentose, and a phosphate group are the two molecules together form the two sides of the DNA. The rungs of the ladder are pairs of 4 types of nitrogen bases.

A piano is a musical instrument which has keys, pedals and strings in which the strings are struck by hammers.