Final answer:
The original phrase in the question conveys a sense of immediacy and surprise effectively, making option (A) 'NO CHANGE' the best choice. Option (C) 'There, right in front of him,' could also work if a change is needed.
Step-by-step explanation:
The question pertains to choosing the best phrase to complete a sentence in a grammatically correct and contextually appropriate manner. Looking at the options given, the current phrase 'He could barely believe his eyes; he had found it at last. Right there in front of him stood the lost city of Atlantis--the aquatic city of myth.' already provides a clear and dramatic introduction to the discovery of the lost city. Option (A) 'NO CHANGE' is already effective as it conveys a sense of immediacy and astonishment. However, if a change was necessary to reduce repetition and maintain flow, (C) 'There, right in front of him,' could be another suitable choice, retaining the surprise and proximity without redundancy. Options (B) 'Immediately present before him' and (D) 'Before him' are less impactful and may not maintain the original intensity of the moment.