What is the primary evidence that dinosaurs existed in the past?

How does the author's purpose in this passage differ from an author writing about her personal struggle living with asthma?

Nasa scientists must work together to make sure that everything is correct and accounted for when launching a shuttle. besides a physicist, what other type of scientist would be in making sure that the shuttle has the appropriate type and amount of fuel to reach its destination?

What form of anesthetic was used for field surgery