Which of the following cells secrete substances like histamine,serotonin,and heparin?

After examining the blood groups of a husband and wife,the doctor advised them not to have more than one child. The blood groups of the couple are likely to be:

The normal percentage of glucose in the blood of man is $0.1\%$. It is found in

What is the principal cation in human blood?

Vitamin $B_{12}$ is helpful:

If the mother has blood group $A$ and the father has blood group $AB$,which of the following blood groups cannot be present in their child?