Which of the following statements about LAN switch is correct?

Which of the following statements about LAN switch is correct?
A . LAN switch is transparent for user, it does not modify the data field of the forwarded frame.
B . LAN switch can still operate normally even when loop exists.
C . LAN switch can detect loop according to the contents of the packet.
D . LAN switch can modify the data field of the forwarded frame when necessary.

Answer: A