Refer to the exhibit. After you applied this EtherChannel configuration to a Cisco ASA, the EtherChannel failed to come up. Which reason for the problem is most likely?
A. The lacp system-priority and lacp port-priority values are the same.
B. The Ether Channel requires three ports, and only two are configured.
C. The Ether Channel is disabled.
D. The channel-group modes are mismatched
you are right, the correct answer is B.
https://www.cisco.com/c/en/us/td/docs/security/asa/asa94/config-guides/cli/general/asa-94-general-config/interface-echannel.html
This is very tricky and I think correct is B. In ASA config guide there is no mention that channel-group modes for physical interfaces cannot be mixed, although no one in their right mind would mismatch modes within same group:
https://www.cisco.com/c/en/us/td/docs/security/asa/asa92/configuration/general/asa-general-cli/interface-basic.html#pgfId-1886959
You can configure each physical interface in an EtherChannel to be:
Active—Sends and receives LACP updates. An active EtherChannel can establish connectivity with either an active or a passive EtherChannel. You should use the active mode unless you need to minimize the amount of LACP traffic.
Passive—Receives LACP updates. A passive EtherChannel can only establish connectivity with an active EtherChannel.
On—The EtherChannel is always on, and LACP is not used. An “on” EtherChannel can only establish a connection with another “on” EtherChannel.