This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Development of nervous system and cerebrum, Subject name: Anatomy
An 80-year-old microbiologist has a cerebral infarction. His speech is limited to expletives, he cannot write but does respond to questions by shaking his head, and he has lower facial weakness on the right side. The lesion is most likely in the: 
Select and explain. 
A. Left frontal lobe., B. Left parietal lobe, C. Left temporal lobe, D. Right frontal lobe
A: Left frontal lobe.
Answer: A: Left frontal lobe. 
Explanation: Lower facial weakness is a localizing neighborhood sign. The Broca speech area is located in the posterior pa of the inferior frontal gyrus (Brodmann areas 44 and 45). Wernicke's speech area is intact as comprehension is intact.