Why do some medieval helmets have crests?

What kind os source would a historian use to get a firsthand account of a past event

An educatethe yuan dynasty was responsible for which of the following: i. improving the road system ii. increasing sea trade with india and south east asia. iii. extending the canal system iv. brutal warfare and ruthless killing of people in order to take over china. a. i & iii c. iv only b. ii only d. all of the above member of the government

Which piece of legislation granted african americans the right to vote