The Great Gatsby is full of symbolism. In this particular passage spends many sentences describing two eyes that seem to be alive. He contrasts the arid area where he is with the very bright colours, blue and yellow, of the eyes. This eyes even seem to have horrifying elements, as he says "they look out of no face" and "pass over a non-existent nose".
The fact that the character personifies these inanimated eyes makes us think that they actually represent something else. They represent a huge, displeased watcher. So, we can say for sure that the correct answer is A: To signify the omniscience of God who looks disapprovingly on what He sees.