The correct answer is - c. Palomares.
The exploring below the ocean's surface has been halted because of the Palomares area. This was due to the infection of this area with nuclear waste. The nuclear waste had big radiation and was very damaging and very risky to the health and lives of the researchers, so the wise decision was to stop the explorations and risk human lives. The exploration of the area will have to wait for some time since the nuclear waste needs quite some time to dispose and the radiation to be lowered down to a degree when it will not be harmful.
