The round third prong on a grounded plug a. creates a short circuit c. completes a circuit to power an appliance b. melts if the current gets too high d. connects to a ground wire

The round third prong on a grounded plug connects to a ground wire. A cheater plug or a three prong adapter is an adapter that allows a NEMA 5-15P grounding type plug to connect to NEMA 1-15 R non grounding receptable.
The purposes of the third prong is to act as a ground connection to improve safety in the event of either a short circuit within an appliance that otherwise might result in delivering shock to the user, or a surge delivered to the appliance due to lightning or another malfunctioning attached to the prong.

By water evaporation from the leaves is created a negative pressure at the top of the tree that promotes the ascension  of the water through channels that are called xylem. there are also two molecule forces that are involved: the intra-water molecules cohesion (water molecules stick to each other) and the adhesion when the water molecules stick to the channels they are running in. this is what enables water to go from the roots to the top of a tall tree.