PLEASE HELPPP ILL MAKE BRAINLIST 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.

According to the federal regulations, which of the following studies meets the definition of research with human subjects? a study of twenty 4th grade classrooms in which researchers ask the schools to systematically vary the time of day reading is taught, and collect weekly assessments of reading comprehension for each child over a three-month period.the collection of data, by a playground designer hired by the superintendent of schools, about the physical dimensions of school playgrounds, presence of fencing, and the kinds of equipment currently provided.a feasibility study for implementing a year-round school program, focusing on economic issues such a facilities utilization and transportation costs.an analysis of aggregate data comparing statewide high school graduation rates provided by the state department of public instruction, using county tax information.