What happens on a Cisco switch that runs Cisco IOS when an RSTP-configured switch receives
802.1d BPDU?

A.
802.1d does not understand RSTP BPDUs because they are different versions, but when a
RSTP switch receives an 802.1d BPDU, it responds with an 802.1d BPDU and eventually the two
switches run 802.1d to communicate.

B.
802.1d understands RSTP BPDUs because they are the same version, but when a RSTP
switch receives a 802.1d BPDU, it responds with a 802.1d BPDU and eventually the two switches
run 802.1d to communicate.

C.
802.1d does not understand RSTP BPDUs because they are different versions, but when a
RSTP switch receives a 802.1d BPDU, it does not respond with a 802.1d BPDU.

D.
802.1d understands RSTP BPDUs because they are the same version, but when a RSTP
switch receives a 802.1d BPDU, it does not respond with a 802.1d BPDU and eventually the two
switches run 802.1d to communicate.