问题：

[单选]

Refer to the network shown below：

R1 and R2 belong to the RIP routing domain that includes the networks 10.20.0.0/16 and
10.21.0.0/16. R3 and R4 are performing two-way route redistribution between OSPF and RIP. Anetwork administrator has discovered that R2 is receiving OSPF routes for the networks
10.20.0.0/16 and 10.21.0.0/16 and a routing loop has occurred. Which action will correct thisproblem？（）

A . Set the OSPF default metric to 20
B . Apply an inbound ACL to the R2 serial interface
C . Configure distribute-lists on R3 and R4
D . Change the RIP administrative distance on R3 to 110
E . Change the OSPF administrative distance on R3 to 110
F . None of the other alternatives apply