Which of the below mentioned entries are required in the main route table to allow the instances in VPC to communicate with each other?

Explanations:

A route with destination 20.0.0.0/0 and target ALL would direct all traffic to an external destination, which is not necessary for internal communication within the VPC.

A route with destination 20.0.0.0/16 and target Local allows all instances in the VPC (including those in the private subnet) to communicate with each other since the entire CIDR block is local to the VPC.

A route with destination 20.0.0.0/24 and target Local would only allow communication within that specific subnet. It does not encompass the entire VPC or allow communication with instances in other subnets.

A route with destination 20.0.0.0/16 and target ALL is not a valid option. The correct target for intra-VPC communication must be Local, not ALL, as ALL is typically used for external traffic routing.