Mark the odd one out.

With reference to the blood in a normal person,which one of the following statements is correct?

The smallest $WBC$ is . . . . . . .

In the child of which one of the following couples,Erythroblastosis fetalis is likely to occur?

During sleep,the rate of $RBC$ formation:

When whole blood is stored with an anticoagulant at $4^{\circ}C$,the $K^+$ ions move out from the $RBC$ into the plasma. The most likely reason for this is that