P HELPPP ITS TIMES Read the excerpt from "The Great Molasses Flood of 1919."

Second, the molasses had been in the tank since July. This was a long time for molasses to be stored in a metal tank. During this time, the molasses began a chemical change. The molasses began making a gas called carbon dioxide. The tank was already too full. The carbon dioxide made matters worse. The gas pushed hard on the steel walls. The result was an explosion. The bottom of the tank blew out.

The cause-and-effect structure describes

a storage tank.
building with steel.
passing time.
a chemical reaction.