The name $Rh$ blood group is derived from

Which are the most active white blood cells?

You are required to draw blood from a patient and to keep it in a test tube for the analysis of blood corpuscles and plasma. You are provided with the following four types of test tubes. Which of them will you $NOT$ use for this purpose?

Persons with $AB$ blood group are called as "Universal recipients". This is due to:

In mammalian $RBC$,the percentage of haemoglobin is

Which blood group is the universal donor and which is the universal recipient?