$12.$ What is a proof of stake $($PoS$)$ consensus mechanism?

A$.$ A mechanism where nodes in the network validate transactions based on the amount of computational work they perform

B$.$ A mechanism where nodes in the network validate transactions based on the amount of cryptocurrency they hold

C$.$ A mechanism where nodes in the network validate transactions based on the number of other nodes that approve them

D$.$ A mechanism where nodes in the network validate transactions based on the number of$$ nodes they are connected to