Exam 300-420 topic 1 question 306 discussion

Actual exam question from Cisco's 300-420

Question #: 306
Topic #: 1

What are two purposes of the RPF check in multicast routing? (Choose two.)

A. to ensure that multicast packets are forwarded if they arrived on the interface used to route traffic back to the source address
B. to ensure that multicast packets are forwarded if they arrived on the interface used to route traffic to the destination address
C. to ensure that multicast packets are dropped if they arrived on the interface used to route traffic to the destination address
D. to ensure that multicast packets are dropped if they arrived on the interface used to route traffic back to the source address
E. to ensure that multicast packets, no matter the interface they arrived on are forwarded out all interfaces