How does a router running RIPv1 determine the subnet mask of the routes that are received in routing updates?

How does a router running RIPv1 determine the subnet mask of the routes that are received in routing updates?

• The subnet mask is included in the routing update
• The router sends a request for the subnet mask to the sending router
• The router uses the subnet mask of the local interface or the default subnet mask for the address class in the routing update
• The router calculates the subnet mask based on the variable length subnetting in its own configuration
• The router defaults to 255.255.255.0 for all updates

Exam with this question: CCNA 2 Exploration v4.0 Chapter 5 Quiz