sentence2_structure: This process<>takes<>the longest amount of time<>usually
sentence1: Introduction People have wondered for a long time why continents have such irregular shapes and why ocean basins, mountain ranges, earthquake belts, and many other features occur where they do.
sentence2: This process usually takes the longest amount of time: an ocean basin forms between two continents.
question: Which of the following processes usually takes the longest amount of time?