【单选题】

A child is to receive intrathecal methotrexate (Folex) for treatment of meningeal leukemia. For which reason would intrathecal administration be selected
A．The child has very poor veins and is unable to receive drugs IV.

B．This drug would be destroyed by gastric acid and so it can't be given by mouth.
C．This drug is poorly transported across the blood-brain barrier, so it's administered intrathecally.
D．Because the drug is rapidly absorbed if given IM, adverse effects may appear more quickly.