All of the following are examples of secondary sources except:
a. a biography of otto von bismarck
b. a letter from a soldier who fought in the napoleonic wars
c. a world history textbook
d. a dvd on the battle of normandy

What is one affect on the australian environment due to the introduction of non-native european rabbits? (a) more grass grew in response to the need of the growing population of rabbits. (b) the rabbits balance out the food chain as they became a natural prey to many predators. (c) the rabbits the land by digging, which caused the soil to spread much needed nutrients. (d) the rabbits out-competed other small animals species and caused them to go extinct.