What causes this behavior?

Refer to the exhibit.

A frame on VLAN 1 on switch S1 is sent to switch S2 where the frame is received on VLAN 2.

What causes this behavior?
A . trunk mode mismatches
B . allowing only VLAN 2 on the destination
C . native VLAN mismatches
D . VLANs that do not correspond to a unique IP subnet

Answer: C

Explanation:

Untagged frames are encapsulated with the native VLAN. In this case, the native VLANs are different so although S1 will tag it as VLAN 1 it will be received by S2.