All of the following mitigation measures were taken after the Great Fire Of London, except which of the following:
a. houses were rebuilt from brick and stone instead of wood and thatch to reduce the risk of fire
b. insurance companies were chartered to provide both insurance indemnification
c. firefighting companies that would attempt to rescue insured properties and a water main system of hollowed tree trunks was laid under city streets to provide water to firefighters, who would dig down to the main and drill a hole to access the water
d. a series of cisterns were put into place to hold water for fire suppression, which are maintained and are still operational today.