Scientists found many different types of fossils in a rock layer, which was dated at 251–299 million years old using an index fossil. In layers directly above that point, scientists found a large decrease in the number of fossils, particularly of marine and insect fossils. When did the extinction event occur?

Which factors add to the greenhouse effect and are caused by human activities?

What is the bill of rights listed in, order

Select the correct answer.look at this nineteenth-century illustration of london. which explanation best relates this illustration to changes in britain in the 1800s? a.factory workers in cities lost their livelihood because of the lack of housingb.industrialization narrowed the inccome gap between landowners and workers.c.the migration of workers from rural to urban areas resulted in overcrowded citiesd.the spread of railways allowed farmers to sell produce far from where it was grown.