It is true that ground water erosion can result in the formation of stalactite and stalagmite in caves.
<u>Explanation:</u>
Stalactite and the stalagmite are the deposits of the minerals where number of minerals get deposited inside the caves and the reason behind this is the water that gets dripped inside the cave slowly and steadily.
The stalactite inside the cave comes from the top of the ceiling of the cave like in the shape of the icicle where as the stalagmite are in the shape of an stalactite but which are inverted. These also form because of the dripping of the water.
Gravitational tidal heating is stronger on Io than any other moon in the Solar System, providing a source of heat that causes its high level of geological activity.
I'd guess b on this one. I don't know the definition of watershed, but the amazon is a pretty big expanse of water "stretching" a long way (albeit that water doesn't stretch).
