Which of the following is a similarity between the huang river and indus valley civilizations?
the use of bronze ritual vessels
a social class system with farmers at the bottom
the exchange of ideas with other cultures
the use of a metal currency 

how were the civilizations of the huang river valley and the nile river valley similar?
both began around 4000 bce.
both arose in desert regions.
both failed to develop a writing system.
both were ruled by dynasties.