Context: Before sunrise on November 14, 1963, the crew of the fishing boat Isleifur II had just finished putting their lines in the ocean off the southern coast of Iceland. As the crew waited to have breakfast, a strong smell of sulfur drifted over the boat. At first, crew members thought that the cook had burned the eggs or that something was wrong with the boat's engine. But when the sun started to rise, the crew saw black smoke billowing from the water a few kilometers away.
The captain of the Isleifur II assumed the smoke was coming from a boat that was on fire, so he sailed closer to try to help. As the Isleifur II approached the smoke, the surface of the sea grew rough. The captain and crew saw flashes of lightning in the column of smoke and glowing pieces of molten rock shooting up out of the water. The captain realized this was not a burning boat. It was a volcano erupting under the water!
Figure: the erupting undersea volcano seen by the sailors on the Isleifur II.
According to the text, what evidence of a volcanic eruption did the captain observe?
A. He heard a report on the radio warning about a volcanic eruption.
B. He saw pieces of molten rock shooting out of the water.
C. He knew his crew had finished putting their fishing lines in the ocean.
Pick the correct answer from the listed options and provide the letter of the selected option.

B