Which is a true statement about EtherChannel?

A. EtherChannel works with 802.1Q to block the redundant lines.
B. EtherChannel can aggregate multiple lines with varying speed.
C. EtherChannel can aggregate interfaces across multiple stand-alone switches.
D. When configured, EtherChannel acts as a single layer 2 connection.

D. When EtherChannel bonds interfaces together, they act as a single Ethernet link. Therefore, layer 2 and layer 3 sees it as a single link.