What best describes the arachnoid mater?

The arachnoid mater is indeed best described as covering the brain with a smooth surface. This is due to its structure, which is a delicate membrane that sits between the more robust dura mater and the inner pia mater. The arachnoid mater plays a critical role in protecting the brain and is complemented by the subarachnoid space beneath it, which contains cerebrospinal fluid. This fluid cushion, along with the smooth surface of the arachnoid mater, helps to absorb shocks, providing additional protection to the brain.

The context provided by the other choices highlights various aspects of the meninges’ layers. While it is true that the arachnoid mater does not have tight connections to neurons (which is more characteristic of the pia mater), nor does it directly follow the intricate shapes of the brain surface as closely as the pia mater does. Additionally, it is composed of a single layer rather than multiple cell layers, distinguishing it from other structures within the nervous system. Thus, the smooth surface of the arachnoid mater is a defining feature, emphasizing its protective role.