Carlos cannot remember Juan Alvarez's name because he was not paying attention when Juan was formally introduced. Carlos' poor memory is BEST explained in terms of failure.

Encoding failure

Explanation:

Encoding is the process where by the human brain turns the information it gathered from the body receptors into a memory. Encoding entails the ability of the brain to store and remember what it has received from body receptor. The brain can encode sounds that it heard or information that the eyes saw.

The inability of the brain to remember the information that it has seen or heard is termed encoding failure.  This can be caused by unsuccessful transfer of of the information to the brain. In the case of Carlos he was distracted and this led encoding failure resulting to him forgetting Juan Alverez's name.

the correct labels are as follows:

a: yellow river

b: himalayan mountains

c: north china plain

d: taklimakan desert