Viruses have an overall structure that is

Options

A. spherical, isometric
B. isometric, icosahedron
C. spherical, helical
D. spherical, isometric, icosahedron, helical

Answer

To answer the question about the overall structure of viruses, we need to analyze the options provided and understand the characteristics of viral structures.

### Step-by-Step Solution:

1. **Understanding Virus Structure**: Viruses are microscopic infectious agents that require a host cell to replicate. They are composed of genetic material (either DNA or RNA) surrounded by a protein coat called a capsid. Some viruses also have an outer lipid envelope.

2. **Identifying Structural Types**: The main structural types of viruses include:
- **Helical**: These viruses have a rod-like or spiral shape. The protein subunits of the capsid are arranged in a helical manner around the nucleic acid.
- **Icosahedral**: This structure is spherical and has 20 triangular faces. The capsid proteins are arranged in a symmetrical pattern.
- **Complex**: Some viruses do not fit neatly into the helical or icosahedral categories and have more complex structures.

3. **Evaluating the Options**: The options provided mention terms like "Aspirical," "Isometric," "Icosahedron," and "Helical."
- "Aspirical" seems to be a typographical error or misunderstanding; the correct term might be "aspherical," which refers to viruses that do not have a defined shape.
- "Isometric" and "Icosahedron" refer to the same structural type, which is the icosahedral shape.
- "Helical" refers to the spiral shape of some viruses.

4. **Conclusion**: Based on the understanding of viral structures, viruses can have various shapes, primarily helical or icosahedral. Therefore, the overall structure of viruses can be described as either helical or icosahedral, depending on the specific virus in question.

### Final Answer:
Viruses have an overall structure that can be helical or icosahedral.