Final answer:
The shape of the nucleocapsid is icosahedral.
Step-by-step explanation:
The shape of the nucleocapsid can be classified into four groups: helical, icosahedral, enveloped, and head-and-tail. Helical capsids are long and cylindrical, while icosahedral capsids are roughly spherical.
An icosahedral capsid is a three-dimensional, 20-sided structure with 12 vertices. It is the most efficient way of creating a hardy structure from multiple copies of a single protein. This shape is used because it can be built from a single basic unit protein, which saves space in the viral genome.
Therefore, the correct answer is icosahedral.