The part of the brain responsible for speech, thought, and memory is the
medulla
cerebellum
cerebrum
thalamus

Cerebrum

The cerebrum is the largest part of the human brain. The cerebrum serves in a multiple variety of functions like logic, memory. emotions, movement and cognition, perception mostly. It has four lobes, the frontal lobe, parietal lobe, temporal lobe and occipital lobe. 

The correct answer is  b)