Viruses are parasitic, having DNA/RNA; but they can be crystallised and lack respiration. therefore they are treated as:

The correct option is both living and non-living beings.

To understand why viruses are classified at the threshold of life, we must look at their dual characteristics:

1. Living Characteristics:
Viruses contain genetic material in the form of DNA or RNA. When inside a host cell, they can replicate, synthesize proteins using host machinery, mutate, and exhibit heredity. These properties align with living organisms.

2. Non-living Characteristics:
Viruses lack cellular structure, protoplasm, and organelle machinery. Outside of a living host cell, they display no metabolism, lack cellular respiration, and are completely inert. Furthermore, they can be crystallized and stored in bottles indefinitely, much like non-living chemical substances.

Because viruses possess properties of both living organisms and non-living matter, biological classification often treats them as a connecting link or border case between both living and non-living beings.