Final answer:
The main idea of the text is that Ben Carson is a renowned neurosurgeon and politician who has contributed significantly to both medicine and government service.
Step-by-step explanation:
The main idea of the text is best represented by option C: Ben Carson is an African-American neurosurgeon and politician who pioneered important brain surgeries and later served as the Secretary of Housing and Urban Development. This option encapsulates the overall achievements of Ben Carson in both his medical career and his later political role. It highlights his pioneering work in brain surgeries, including separating conjoined twins, and acknowledges his service as Secretary of Housing and Urban Development, thereby covering the major aspects of his professional life.
Options A and D focus on specific aspects of Carson's life and do not encompass the full scope of his achievements. Option B is also specific, mentioning a particular initiative during his political career but does not provide a comprehensive summary of his major life accomplishments.