A.The IOS default is for a last-hop router to trigger a switch to the shortest path tree as soon as a new source is detected on the shared tree.
B.The IOS default is for every one of the routers on the shared tree to trigger a switch to the shortest path tree as soon as a new source is detected on the shared tree.
C.The default behavior of switching to the shortest path tree as soon as a new source is detected on the shared tree can be disabled by setting the value in the ip pim spt-threshold command to "infinity."
D.The default behavior of switching to the shortest path tree as soon as a new source is detected on the shared tree can be disabled by setting the value in the ip pim spt-threshold command to "zero."

A.The packet will loop between R1 and R2.
B.It is not possible to set the administrative distance on a summary to 255.
C.The packet will be forwarded to R2， where it will be routed to null0.
D.The packet will be dropped by R1， since there is no route to 192.168.3.1.