Studying the difference in prevalence of drug-related violence in states with and without medical marijuana use is an example of an ecologic study. a. Trueb. False

answer : haversian

[explanation: -(compact bone is organized as parallel columns, known as haversian systems, which run lengthwise down the axis of long bones. these columns are composed of lamellae, concentric rings of bone, surrounding a central channel, or haversian canal, that contains the nerves, blood vessels, and lymphatic system of the bone)]

the cost of mining is extremely low compared to the money earned from mining, creating income to improve the environment.

wegner's theory did not explain how the continents could move

explanation: