Why was the aboriginal population reduced when european colonists settled in australia (a) europeans brought animals with them (b) most europeans settled in aboriginal land (c) harsh environment of the outback killed many natives (d)europeans brought diseases with them

The answer would be D. Europeans brought diseases with them. 
This is true for most instances when Europeans settled in new lands, the local population was exposed to disease that they brought with them and killed off a large portion of them. I hope this helps :)

This question is an opinionated one, and we don’t know anything about the module or anything, thus we can not answer it. but if you are having trouble on what it is asking basically it is just asking to (using your knowledge on the topic) say which topics you were most interested and which were the most challenging.hope this : p

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