Give one property because of which viruses are regarded as being on the borderline of living and non-living

Viruses are regarded as being on the borderline of living and non-living because it exhibits characteristics of both living and non-living organisms. Inside a host, the virus can act as a living organism using the host's cellular system while outside the host, the virus crystallizes that makes them incapable of conducting metabolic activities. 

Answer: the dna polymerase checks for errors in dna to prevent replication mistakes.
i hope this !