What is causing this issue?

Refer to the exhibit.

Traffic is not passing through IPsec site-to-site VPN on the Firepower Threat Defense appliance.

What is causing this issue?
A . Site-to-site VPN peers are using different encryption algorithms.
B . Site-to-site VPN preshared keys are mismatched.
C . No split-tunnel policy is defined on the Firepower Threat Defense appliance.
D . The access control policy is not allowing VPN traffic in.

Answer: C