The correct option is 2 only
Explanation
The cerebrum forms the major part of the human brain and is structurally divided into two distinct halves known as the cerebral hemispheres.
Statement 1 is Incorrect: The cerebrum is divided longitudinally into two halves, the left and right cerebral hemispheres, by a deep longitudinal cleft (fissure). This physical separation distinguishes the two sides of the brain.
Statement 2 is Correct: The two cerebral hemispheres are connected by a tract of nerve fibres called the corpus callosum. The cerebellum is a distinct structure located at the back of the brain, below the cerebrum, responsible for coordination and balance; it does not connect the two cerebral hemispheres.
Statement 3 is Incorrect: The outer layer of the cerebral hemispheres, known as the cerebral cortex, is not smooth. It is highly convoluted, featuring prominent folds (gyri) and grooves (sulci). These folds significantly increase the surface area of the brain, allowing for a higher density of neurons within the cranial cavity.
Key Takeaway: The cerebral hemispheres are separated by a deep longitudinal cleft, connected internally by the corpus callosum, and characterized by a highly folded outer layer called the cerebral cortex.