[Manas Ranjan Mallick]

I am not a professional teacher in true sense. Here the question is whether a or an will be used before 100. 100 is pronounced as hundred. The beginning alphabet 'h' is a consonant and sounds like a consonant. So the special rule i.e. if the beginning alphabet sounds like a vowel, we use an. If the same alphabet sounds like a consonant we use a. Example: an umbrella. a unit. an hour, a horse. So here since beginning of 100 sounds like a consonant 'a' will be used. As such "The company is a 100% ESOP company." is correct.