Final answer:
The correct command for enabling RIPv2 to receive and send v1 updates is update-rip compatibility v1. Hence the correct answer is option 3
Step-by-step explanation:
The correct command for enabling RIPv2 to receive and send v1 updates is update-rip compatibility v1.
RIPv2, or Routing Information Protocol version 2, is an improvement over RIPv1 and includes several enhancements. By setting the compatibility to v1, the router will be able to communicate with routers that are still using RIPv1.
For example, if you have two routers, Router A and Router B, and Router A is sending updates using RIPv1, while Router B is using RIPv2, you can enable v1 compatibility on Router B to receive and understand the updates sent by Router A.
Hence the correct answer is option 3