Technically A and B, but A is more true, so it is the 'correct' answer.
The environment selected is favorable to ponies with longer legs.
... 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.
Answer:
It becomes something like that
It becomes firm/turgid if it were an animal cell it would've burst but the cell wall prevents it from doing so.