Ans.
Vaccines represent a biological preparation, prepared by inactive or dead for m of microbes or their pathogenic components to develop acquired immunity against those microbes. Vaccines stimulate antibody producing immune cells or B lymphocytes to provide immunity against the particular pathogen.
These cells form antibody producing memory B-cells that remember that pathogen and produce more effective antibodies against it with a faster rate in future infections.
As the woman has received vaccine for measles during her childhood, she will show presence of measles-specific antibodies in her blood as evidence that the vaccination has provided her immunity against measles. Thus, the correct answer is option d).