Answer: The condition necessary for a virus to attack a host cell is that the viral DNA or RNA must have a sequence that is recognized by the ribosomes of the host cell (E).
Step-by-step explanation:
The ribosomes in the host cell are responsible for protein synthesis. When a virus enters a host cell, it hijacks the cell's machinery to replicate itself. In order to do this, the viral DNA or RNA needs to be recognized by the ribosomes so that they can start translating the viral genetic material into viral proteins.
Once the viral proteins are synthesized, they can carry out various functions, such as puncturing the membrane of the host cell (C) or causing the host cell to burst (B). However, these conditions are not necessary for a virus to initially enter the host cell.
The key sequence (A) is not necessary for the virus to enter the host cell. It is the recognition by the ribosomes (E) that allows the virus to utilize the host cell's machinery.
Similarly, the shape of the virus (D) is not necessary for it to enter the host cell. It is the recognition of the viral genetic material by the ribosomes that determines whether a virus can successfully infect a host cell.