It is B. a question based on observations
I think so
About 60% of natural conceptions fail to implant properly. One of the reasons may be the failure of the embryo to generate Trypsin, a chemical which induces a receptive environment in the uterus in order for the fetus to be implanted. The excess or lack of chromosomes of the fertilized egg may also be a factor in implantation failure. A weak immune system of the woman may also be an important factor.
When a phage comes in contact with a bacterial host, it attaches itself to the receptors at the outside surface of the cell. Once secured, the phage injects its DNA or RNA inside the cell through endocytosis. Once inside, the host will change according to the DNA or RNA injected.