Which is true only about emails and not letters?

They are more personal.
They are easier to write.
They include a written signature.
They already have the date included.

When should you use encyclopedias such as wikipedia? a. never, it is not appropriate to use this source in college b. it can you get an overall understanding of the subject matter but is not considered a college-level source c. as long as wikipedia isn't the only source, it is always appropriate to use this source

(1) fire extended humans’ geographical boundaries by allowing them to travel into regions that were previously too cold to explore. (2) it also kept predators away, allowing early humans to sleep securely. (3) fire, in fact, has been a significant factor in human development and progress in many ways. (4) other obvious benefits of fire are its uses in cooking and in hunting. (5) probably even more important, however, is that learning to control fire allowed people to change the very rhythm of their lives. (6) before fire, the human daily cycle coincided with the rising and setting of the sun. (7) with fire, though, humans gained time to think and talk about the day’s events and to prepare strategies for coping with tomorrow. the sentence that expresses the main idea is: (type the number of the sentence. then click “go.”)

American history (is, are) studying the american colonies.