Answer:
There is a greater population density on the SE coast because it has more access to water.
Step-by-step explanation:
A is not correct because the wombats have absolutely no influence on the human settlements and their population.
B is not correct because this part of the Australian coastline doesn't have deserts.
C is not correct because the SE coast doesn't have a tropical climate, but it is the northeast coast that has this type of climate.
D is correct because the SE coast has more access to water, and this is due to the milder climate, mountain ranges, and higher precipitation, leading to many more rivers and streams in the area, thus an abundance of fresh water, not just access to saline water.