Answer:
a. are called gyri
Explanation:
Gyri -
On the cerebral surface in the brain , a system of folds and ridges are referred to as the gyri ,
the folding on the surface increases the surface area i.e. larger cortical surface area and greater cognitive function
The gyri is the ridge and the groove between two gyri is called the sulci .
The pattern of folds indicates some specific regions of the cerebral cortex .
