I have read some articles of Hammurabi's code and I believe the correct answer is B.
A tough era, and lasted many years
Wood being softer than coal is a physical property. Any chemical property has to deal with a change in somethings composition. When would is burnt, rotted, or not rusted, it is because there is some form of chemical reaction (Or lack thereof) inside of the wood. The property of being softer, however, does not come about by changing what wood is.
David Sarnoff and William Paley
very strong central government; little regional or state control= unitary
power shared between central government and regional or state= federal
weak central government; strong state or regional government = confederate