Traveling at the speed of light near the AC direction, the observer on the train measured that the height of the tower was greater than the distance between adjacent towers. After starting from B, the observer on the train saw the light reflected by A and C. Because the train moved closer to C and was far away from A during this time, the reflected light of C first reached the observer on the train and was first illuminated when it saw C, so C was chosen.

So the answer is: greater than C.