The magnetic field of a bar magnet is the strongest at either pole of the magnet. It is equally strong at the North Pole when compared with the south pole. So I would say the answer is A.
A green roof produces heat loss
... termed "hypotonic," meaning less solids (or more diluted) than inside the cell. For fluid movement in/out of cells, water will diffuse (via osmosis) from the hypotonic solution to the hypertonic one, assuming a permeable barrier (i.e. cell membrane) allows it. With this case, water will flow into the cell from outside.
The answer to this problem is crayfish