Option (a) is correct. Other statements can be corrected as viruses
are acellular entities and contain either DNA or RNA. They replicate using the
replication proteins of their host cell. The protein shell of virus is called capsid, it
encloses the genetic material of the virus. It protects the nucleic acid from digestion
by enzymes. The polymerase genes of virus are expressed early in the cycle of
virus but capsid and tail proteins are expressed later.