The initials will still be 4 feet above the ground.
Trees do not grow from the bottom up. At the branch tips there is meristem tissue, so called the apical meristem. Trees grow in height from these apical meristems, so trees grow from the top and the initials on the bottom of the tree will stay at the same height above the ground.
Acetylcholine, sometimes shortened to ACh.
The correct answer is B. unicellular.
Dinoflagellates are unicellular or multicellular, producers, and autotrophs, and apple trees are multicellular, producers, and autotrophs. All plants have numerous cells in them, so they can never be unicellular. The remaining characteristics they share with less complex organisms such as dinoflagellates.
The guard cell is responsible for controlling the size of the stomata in leaves. These do so as a result of an interaction between potassium ions and water in and around the cells. When potassium ions accumulate inside the guard cells the water potential inside these cells is lower than that of the outside and as a result, water has to be taken in. This makes the guard cells turgid which in turn stretches them and results in the opening of the stomata. Meanwhile, when potassium ions accumulate outside the cell, the opposite scenario results. Water from inside the cell moves out, making the guard cells flaccid, thus causing these to cover (and effectively close) the stomata.