As a frame leaves a Layer 3 device，the Layer 2 encapsulation information is changed from what it was when it entered the device. For what two reasons can this happen？（）

• A、The data is moving from 10BASE-TX to 100BASE-TX.
• B、The WAN encapsulation type has changed.
• C、The data format has changed from analog to digital.
• D、The source and destination hosts are in the same subnet.
• E、The source and destination MAC addresses have changed.