Final answer:
The brain, particularly areas like Broca's and Wernicke's regions, is responsible for controlling language expression and speech muscle movements.
Step-by-step explanation:
The brain controls language expression and directs the muscle movements involved in speech. Notably, certain areas of the brain are responsible for different aspects of language. One such area, known as Broca's area, is specifically associated with the production of speech, while Wernicke's area is essential for the comprehension of language. These areas, along with other neural circuits in the brain, coordinate to produce speech and language.
The brain is the source of our conscious cognitive processes including perception, interpretation, imagination, memory, and crucially language. Motor functions such as language are managed by the brain and its complex systems, aided by the motor cortex, cerebellum, and the basal ganglia. Moreover, the brain stem plays a vital role in controlling many involuntary functions such as breathing and heartbeat.
Therefore, in response to the question, the correct answer is 1) Brain.