Which of the following best describes the D orbital shape?

The D orbitals are best characterized by their "double peanut" shape, which reflects the complex distribution of electrons within these orbitals. Specifically, the D orbitals can be visualized as having four lobes arranged in a four-leaf clover configuration for most of the D orbitals, which contribute to the "double peanut" description.

In contrast to the spherical shape of the S orbital or the dumbbell shape of the P orbitals, D orbitals have more intricate geometries that arise from the angular momentum associated with the electrons in these orbitals. The D orbitals can also exhibit orientations that involve combinations of spherical harmonics, which leads to their unique shapes.

The other options do not accurately depict the D orbital shapes. A single sphere describes S orbitals, representing the simplest orbital shape. A pair of spheres does not correspond to any typical orbital shape in quantum chemistry. Finally, a linear structure is characteristic of certain molecules or configurations in molecular orbitals but does not apply to the geometry of D orbitals. Thus, the "double peanut" shape is the most accurate representation of D orbital geometry.