How does tree ring dating show wet and dry periods?

Examine these two paintings that depict famous events from american history. the image on the left, painted in 1940, shows the signing of the u.s. constitution in 1787. the image on the right, painted in 1836, shows the american victory at the battle of yorktown in 1781.which of these paintings should be considered a secondary source?

In their competition for power nations raced to

56: 58 the assembly line was a system through which items were mass-produced in a flow.