Question

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

Answer 1

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 :)

Answer 2

the answer is d 
hope it helps 
i did the same quiz it was right trust me