Final answer:
The incidence of cerebral palsy has remained relatively stable since the 1960s. Cerebral palsy is a condition caused by brain injury around the time of birth, affecting motor functions and muscle control, ranging from mild to severe symptoms.
Step-by-step explanation:
The incidence of cerebral palsy (CP) has remained relatively stable since the 1960s; therefore, the correct choice would be 'c. remained the same.' It's important to note that cerebral palsy is caused by injury to the developing brain either before, during, or shortly after birth. While CP can be more common in babies with a low birth weight, the precise cause of the brain injury is often unknown.
Cerebral palsy primarily affects the parts of the brain that control body movement, leading to symptoms ranging from mild muscle weakness to more severe challenges, such as difficulty walking and talking. Presently, there is no cure for cerebral palsy, but early intervention and supportive treatments can improve outcomes for individuals with this condition.