In Hyper-V what is the feature that allows a virtual machine to raise or lower its memory based on demand?

In Hyper-V what is the feature that allows a virtual machine to raise or lower its memory based on demand?

• Dynamic Memory
• Demand Based Memory Scaling
• Memory Overcommit
• Memory Optimization 

 EXPLANATION

https://technet.microsoft.com/en-us/library/hh831766(v=ws.11).aspx
Hyper-V utilizes Dynamic Memory which allows the VM admin to set a value for startup memory, minimum memory, maximum, and a memory buffer. This allows the host to reserve or release memory for the virtual machine based upon the demand of the applications running inside the VM.