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

• A
  $RBC$ haemolyses and hence leakage of $K^+$ ions
• B
  $K^+$ ions become more mobile at $4^{\circ}C$
• C
  Active transport ceases resulting in ionic equilibrium
• D
  The anticoagulant attracts the $K^+$ ions into the plasma