Question

the subarachnoid space is just outside the
arachnoid mater.
pia mater.
neocortex.
central canal.

Explanation:

The subarachnoid space is located between the arachnoid mater and the pia mater. It is just outside the pia mater. The arachnoid mater is above the sub - arachnoid space, and the neocortex and central canal are not related to the immediate location of the subarachnoid space.

Answer:

pia mater.