The death of a spouse is usually regarded as the most difficult of all deaths

In 2007, Alex the African gray parrot died. He was an important part of the work conducted in _____

A) cognition and communication research B) animal genetics C) motivation D) recall and recognition

The organization of the human cortex is typically composed of ___ layers and columns containing ___ neurons

a. 6, more than 500 b. 5, 80–100 c. 5, more than 500 d. 6, 80–100