Final answer:
Option A). Gap junctions in animal cells and plasmodesmata in plant cells are connections between neighboring cells that allow for the diffusion of small signaling molecules and ions. These channels enable cells to communicate and coordinate their response to signals.
Step-by-step explanation:
The connections between adjacent cell plasma membranes are known as gap junctions in animal cells and plasmodesmata in plant cells. Small signaling molecules known as intracellular mediators are able to diffuse between the two cells through these fluid-filled channels. Large molecules, like proteins and DNA, cannot fit through the channels, but small molecules, like calcium ions (Ca2+), can travel between cells. While allowing the cells to stay autonomous, the channels' specificity allows for the fast and simple transmission of signals. In order for a group of cells to coordinate their response to a signal that only one of them may have received, signaling molecules must be transferred in order to communicate the current state of the cell that is directly adjacent to the target cell. In plants, plasmodesmata are ubiquitous, making the entire plant into a giant communication network.