How do historians conduct credible research?

Why are primary sources important when studying historical events

Which of the following is an example of a concurrent power? a. when a group of states work together to regulate interstate commerceb. when a federal law enforcement agency state policec. when a state creates a treaty with a foreign governmentd. when a local government collects taxes on imports

What are your thoughts about " the attacking on the twin towers". in your own words a little paragraph its for a project i am doing and i want to get intel from other people so that i can put it on my poster. for anyone who gives me there opinion on it : ) enter you name when you type the paragraph more than one person to respond.