The single most deadly entity on the planet is the

O virus

O bacteria

O bacteriaphage

Ophage

both a and be

O both c and d

None of the above

The single most deadly entity on the planet is the virus

Explanation:

Virus is the most deadliest microorganism as a result of their replication factor and ability to change protein coat which resist drug therapy on it. Also the time taken for the replication is lesser and rapid.