Hence When we eat food it closes but when we talk While eating the epiglottis would remain open and the food may enter windpipe which may trigger violent coughing to clear the food material out of trachea or may get serious by Chocking and may be fatal. That is why it is not advised to talk while eating
These are things that won't be going away. Natural gasses and fossil fuels will likely run out someday or become much harder to find. When you use these sources of energy, they won't be going away and therefore will be sustainable because we can always continue using them.
