Final answer:
The default version of Routing Information Protocol (RIP) when enabled is RIPv1, which lacks support for subnet information and CIDR. The correct answer is 1.
Step-by-step explanation:
The default version of RIP (Routing Information Protocol) when enabled is RIPv1. This protocol is a distance-vector routing protocol used in local and wide area networks.
RIPv1 is the original version of RIP and uses classful routing, which means it does not support subnet information or CIDR (Classless Inter-Domain Routing). The newer version, RIPv2, introduced support for classless routing and other enhancements but by default, when RIP is enabled on a router without specifying the version, it will default to RIPv1. Therefore the correct option is 1.