Why do simple animals, such as flatworms and sea stars, survive without special circulatory systems but more complex organisms, like reptiles and humans, cannot?

Flatworms get most of their oxygen through diffusion.

Explanation:

the correct answers are:

a - pacific plate;

it is the biggest oceanic tectonic plate. surrounded on all sides by continental tectonic plates, it is submerging and gradually becoming smaller and smaller.

b - north american plate;

huge continental plate, occupying big portion of the northern hemisphere.

c -eurasian plate;

alongside the north american plate, it is one of the two dominant continental plates in the northern hemisphere.

d - indian plate;

a small continental plate, that has been part of gondwanaland initially, but after the break up of it, moved towards northeast and pushed into the eurasian plate that was once part of laurasia.