**Explanation:**

**1. Viruses and their metabolic machinery:**

Viruses are considered as obligate intracellular parasites, meaning they require a host cell to replicate and multiply. Unlike living organisms, viruses lack the metabolic machinery required for independent energy generation and synthesis of macromolecules such as proteins, carbohydrates, and nucleic acids.

**2. Energy generation:**

a) **Protein synthesis:** Viruses lack the ribosomes necessary for protein synthesis. Ribosomes are cellular structures that translate the genetic information encoded in mRNA into specific amino acid sequences to synthesize proteins. As viruses lack ribosomes, they are incapable of synthesizing proteins on their own.

b) **Carbohydrate synthesis:** Carbohydrates are synthesized by living organisms through complex metabolic pathways. These pathways involve enzymes and various cellular machinery. However, viruses lack the necessary enzymes and metabolic machinery to synthesize carbohydrates.

c) **Alcohol synthesis:** Alcohol is a specific type of organic compound that is produced by living organisms through fermentation processes. Viruses, being acellular entities, lack the necessary cellular machinery for fermentation or any other metabolic pathways to synthesize alcohol.

**3. Viral replication:**

When a virus infects a host cell, it hijacks the cellular machinery of the host to replicate its genetic material and produce viral proteins. The viral genetic material (DNA or RNA) is used by the host cell's machinery to synthesize viral proteins. These proteins are then assembled to form new viral particles, which can be released to infect other cells.

**4. Host cell dependency:**

Viruses depend entirely on the host cell's metabolic machinery for energy generation and synthesis of macromolecules. The host cell provides the necessary energy and building blocks for viral replication and protein synthesis.

In conclusion, viruses lack the metabolic machinery required for energy generation and synthesis of macromolecules such as proteins, carbohydrates, and alcohol. They rely on host cells to provide these essential components for their replication and survival. Therefore, the correct answer is option 'A' - viruses largely lack the ability to synthesize proteins.

It's not iwanosky as he said that viruses are filterable but mayer suggested the infectious nature of TMV, hence the given option is correct