Dark energy is a theoretical repulsive energy that causes the acceleration to the expansion of the universe. Among the choices, the nearest answer would be D. Dark energy can also be defined as a new form of energy, that is a dynamic field that fills up space but has an effect opposite to that of normal energy.
Power grid
All the poles and wires you see along the highway and in front of your house are called the electrical transmission and distribution system. Today, generating stations all across the country are connected to each other through the electrical system (sometimes called the "power grid").
You have to figure it out