Which two of these statements correctly describe classic PIM-SM? (Choose two.)

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."

Explanation:
ip pim spt-threshold [vrf vrf-name] spt-threshold {kbps | infinity} [group-list access-list]

To configure when a Protocol Independent Multicast (PIM) leaf router should join the shortest path source tree for the specified group

infinity Causes all sources for the specified group to use the shared tree.