[A] bringing [C] having
[B] obtaining [D] purchasing

A．Megalodon, the largest shark, is extinct
B．Megalodon is not extinct but just out of reach
C．Megalodon was 52 feet long and had a jaw 7 or more feet wide
D．Megalodnn lived between several million years ago

A．To listen for changes in ocean structure.
B．To listen for changes of ocean currents or volcanic activity.
C．To make sure whether there was a giant squid deep in the ocean.
D．To follow the track of the Soviet warships under water.