Final answer:
The amygdala is the part of the brain that is significantly active when viewing facial expressions of fear, especially important for processing emotions and memory consolidation linked to fearful stimuli.
Step-by-step explanation:
The part of the brain that is especially active when viewing facial expressions of fear is b) Amygdala. This region has received significant attention for its role in processing emotions, particularly fear and anxiety. The amygdala is made up of various nuclei, including the basolateral complex, which is crucial for classical conditioning, and the central nucleus, which impacts attention and regulates the autonomic and endocrine systems. It is also involved in memory consolidation, the process of transferring new learning into long-term memory, especially when the learning event is emotionally arousing.