Answer :
Viruses aren't able to respond to stimuli when outside of a host cell because outside host cells, viruses are dormant and sometimes even considered dead. Only when a virus starts reproducing in a cell can it weakly respond to stimuli.
Viruses they do not respond to stimuli when they are outside host.
This is because outside viruses and hosts are being dormant. They can be even be considered as dead.
Virus can only respond to stimuli only when they start reproducing in a cell.
