What did the Zhou dynasty create with its new types of ironwork?
They developed stronger weapons.
They built stronger and safer buildings.
They turned the iron into steel for sharp swords.
They used the iron to build ships for fighting wars.

The answer B

:The Zhou Dynasty was able to hold absolute power until 776 BC when the Warring States Period began in China. ... A new form of iron replaced meteoric iron during the Chinese Iron Age called pig iron, which was easier to work with and malleable.

they build things useful

Explanation:

even though you have attached neither the chart nor the generalizations, i have located them online. the right answer is d, since they are asking you about a generalization. you can only infer from the chart that between 2008 and 2009 the number of employed workers decreased significantly (from over 115 millions to 107 millions approximately), which signals some type of economic crisis.