Switch SW$1$ sends a frame to switch SW$2$ using $802\mathrm{.}1$Q trunking. Which of the answers describes how SW$1$ changes or adds to the Ethernet frame before forwarding the frame to SW$2?$

Inserts a $4-$byte header and does change the MAC addresses

Inserts a $4-$byte header and does not change the MAC addresses

Encapsulates the original frame behind an entirely new Ethernet header

None of the other answers are correct