The sentence needs an adjective describing the audience as being held in fascination while they listened to him. The correct word for this is spellbound, meaning so fascinated that you cannot think of anything else.
Checking the options: Spellbinded is not a real word, spellbind is the base verb form and does not fit as an adjective here, spellbinding is an adjective but it describes the person or thing causing fascination, not the listeners, and Spellbou is an incomplete or misspelled form.
None of the four options spell the correct word, spellbound, accurately. This question is defective. Among the given choices, option D, Spellbou, is treated as the closest attempt at the intended word, so it is marked as the answer, but strictly speaking no option is fully correct.