Establish/Maintain a Formal Explanatory Style Practice Test

The passage is intended for a school website’s informational page about earthquakes: “An earthquake occurs when stress builds along a fault and is released suddenly. Seismic waves travel through Earth and may cause ground shaking. I think it is scary when the ground moves.” Which change best maintains formal, objective style?

The writer is drafting a formal social studies report about the three branches of government. Which sentence should be revised because it is too informal?