None of the above. An "Isthmus" (ISS-muss) is a strip of land separating two bodies of water.
A canal
An example of a beam bridge is Chesapeake Bay bridge-tunnel Site: http://www.pbs.org/wgbh/buildingbig/bridge/index.html
beam and tunnel
Hampton Roads Bridge-Tunnel was created in 1957.
That would be the tunnel part of the Chesapeake Bay Bridge-Tunnel.See related link.That would be the tunnel part of the Chesapeake Bay Bridge-Tunnel.See related link.That would be the tunnel part of the Chesapeake Bay Bridge-Tunnel.See related link.That would be the tunnel part of the Chesapeake Bay Bridge-Tunnel.See related link.
Louis-Hippolyte Lafontaine Bridge-Tunnel was created in 1967.
Monitor-Merrimac Memorial Bridge-Tunnel was created in 1992.
a sound
Bridge and Tunnel Officers (TBTA Officers) are the Police force for the Triborough Bridge and Tunnel Authority. TBTA Officers have Peace Officer powers throughout NYS on duty and off duty.
Bridge + tunnel = brunnel
No, there is no bridge between the United Kingdom and mainland Europe. There is a tunnel called the Channel Tunnel.
Tunnel vision.