City A is the closest to sea level with a location of -0.25 meters relative to sea level.
The city closest to sea level is City A, with a location of -0.25 meter relative to sea level.
This means that City A is 0.25 meters below sea level.
To determine which city is closest to sea level, we look for the value with the least absolute value.
The absolute value of -0.25 is 0.25, which is smaller than the absolute values of the other cities' locations (7/4, -3/2, and 0.5).
Therefore, City A is the closest to sea level.