What is the origin of the word "Hello"?

Option A 'hallo' is indeed considered a correct answer. The word 'hello' emerged in the 1800s as a variation of 'hallo', 'holla', or 'holla', which were themselves alterations of 'holla' - a exclamation meaning 'stop!' or 'attention!'. The use of 'hello' as a standard telephone greeting was popularized by Thomas Edison. Option B 'hola' is Spanish, not English etymology. Options C and D are incorrect spellings.