The sentence describes men, women and children wearing some type of gown. 

The options list words that could describe the gowns.

We need an order that flows nicely when read out loud.

• “White flowing exceedingly beautiful gowns” (D) sounds a little awkward.
• “Flowing exceedingly white beautiful gowns” (E) has too many adjectives grouped
• “White beautiful exceedingly flowing gowns” (A) also seems off.
• “Exceedingly flowing white beautiful gowns” (B) piles on too many adjectives
• Only “Exceedingly beautiful white flowing gowns” (C) reads smoothly in order

Therefore, to nicely describe the outfits when read aloud, choice C “Exceedingly beautiful white flowing gowns” best completes the sentence while sounding pleasant to the ears!