Mass extinctionsa. are an example of 'uniformitarian' principles in geology b. are often triggered by magnetic field c. reversals occur at regularly spaced intervals in the geologic record d. denote a relatively sudden, global decrease in the diversity of life forms. e. are usually caused by a tsunami

What is the most effective approach the government can take to keep the air clean? create and enforce regulations that limit fossil fuel burning by industries use funds to understand why smoke and mold are causes of outdoor air pollutants educate people about the threats to outdoor clean air from visible forms of air pollution modify regulations under the clean air act by including expensive options to reduce air pollution