Final answer:
A defective phage cannot properly replicate within a new target cell typically because it has lost some of its genetic material.
Step-by-step explanation:
A defective phage is typically a virus that has lost some of its genetic material or has undergone some form of mutation or alteration that impairs its ability to replicate. While the phage can still infect a host cell, it may not be able to fully replicate or produce new virions capable of infecting new cells. This defect could occur in various ways, such as by the loss of genes necessary for the synthesis of vital components of the phage or by the inability to package its genetic material properly.
The closest option to the correct answer among the choices given is B) A virus that has lost some of its genetic material, and therefore cannot replicate within a new target cell. This means it lacks some of the components that are necessary for the production of new virus particles within the host cell.
Bacteriophages, like the T4 or the λ (lambda) virus, rely on either the lytic or lysogenic cycle to reproduce within bacterial cells. If a phage is defective, it could disrupt this replication process and, hence, the virus's life cycle within the bacterial host.