Which antibody is obtained by the fetus from the placenta to provide immunity?

Virus-infected cells secrete proteins called

Assertion $A$: Innate immunity consists of various barriers. Reason $R$: Exposure to a pathogen is required for the stimulation of innate immunity. Which option is correct for Assertion $A$ and Reason $R$?

In the list given below,how many are secondary lymphoid organs?
Thymus,Spleen,Bone marrow,Tonsil,Appendix

What happens in active acquired immunity?

$B$-lymphocytes produce an army of proteins in response to pathogens entering our body to fight them. These proteins are called.........