Final answer:
Enlarging a computer's memory is synonymously referred to as upgrading the computer's memory. It improves the computer's performance by increasing its data processing and storage capabilities.
Step-by-step explanation:
The synonym for "need to ENLARGE the computer's memory" is B) Upgrade the computer's memory. Enlarging or increasing the memory is commonly referred to as an upgrade because it enhances the computer's performance by allowing it to process more data concurrently or store more information. This is not to be confused with reducing, ignoring, or monitoring, which all have different meanings: to reduce would mean to decrease the memory size, to ignore would mean not to pay attention to the memory, and to monitor would mean to keep an eye on or check the status of the computer's memory without necessarily making changes to its size.