Answer:
a. Broca's area
Step-by-step explanation:
Broca's area: Broca's area is found in the frontal lobe of an individual's brain and is involved in the eloquent aspects of the written and spoken language by a person. It is responsible for speech production and controls the motor functions which are involved in the process of producing a particular speech.
An individual who is dealing with the damaged Broca's area finds difficulty to put different words together while producing speech yet can understand the words.
In the question above, Bill's difficulty speaking is due to brain damage to Broca's area.