【单选题】

1The cerebral cortex of the human brain is divided into two hemispheres that are linked by a thick band of fibers called the corpus callosum.Each hemisphere has four discrete lobes, and researchers have identified a number of functional areas within each lobe. The left hemisphere has areas for controlling speech, language, and calculation, while the fight hemisphere controls creative ability and spatial perception. This centering of functions in specific areas of the brain is known as lateralization.

2Much of our knowledge about brain lateralization comes from studies of "split-brain" patients, people with a damaged corpus callosum. In one experiment, a subject holding a key in his left hand, with both eyes open, was able to name it as a key. However, when the subject’s eyes were covered, he could use the key to open a lock, but was unable to name it as a key. The center for speech is in the left hemisphere, but sensory information from the left hand crosses over and enters the fight side of the brain. Without the corpus callosum to function as a switchboard between the two sides of the brain, the subject’s knowledge of the size, texture, and function of the key could not be transferred from the fight to the left hemisphere. The link between sensory input and spoken response was disconnecteD、
Which sentence below best expresses the essential information in the highlighted sentence in paragraph 1A．Each half of the brain consists of four types of tissues that are identified by their size and location.
B．The brain’s two hemispheres each have four separate parts, and each part controls several functions.
C．There are a number of functional centers in the brain, and these can be divided into four main groups.
D．Research has shown that the brain controls four basic functions, each with a number of variations.