Following are the statements made about major functions of some of the neuroglia in normal condition:

A. Oligodendrocytes help maintain K⁺ level, and contribute to the blood-brain barrier.

B. Microglia are capable of movement and phagocytosis of pathogens and damaged tissue.

C. Astrocytes produce the myelin sheath to electrically insulate neurons of the CNS.

D. Ependymal cells which are ciliated are involved in circulation of cerebrospinal fluid.

Which of the following options represents the combination of all INCORRECT statements?