The average depth of the oceans is about 4300 meters (m). Why do most of the marine organisms live in the top 200 m of the ocean waters?
a. Marine organisms thrive in high salinity, and the water near the surface has the highest salinity.
b. Marine organisms are healthier in the coldest waters, and the water near the surface is the coldest.
c. Many marine organisms are consumers living where food is abundant, and the water near the surface
has many producers.
d. Many marine organisms better survive in water with a low pH, and the water near the surface has the lowest pH
due to high carbon dioxide levels.

Out of the seven main animal groups (fish, mammals, birds, insects, reptiles, amphibians, and arachnids), how many contain members with internal backbones? a. 5 b. 3 c. 7 d. 1

On a recent expedition to a remote region of northern canada, scientists uncovered skeletal remains from about 100,000 years ago. surprisingly, all the skeletal remains, which included many species from differing biological families and spanned about two thousand years, showed evidence of experiencing temperatures in excess of 1000 degrees fahrenheit (or 538 degrees celsius). which of the following, if true, best explains the apparent paradox between the cold environment and the evidence of the bones experiencing hot temperatures? (a) chemical changes that naturally occur during the process of decay in only one north canadian species produce the same evidence of the species' skeletons being exposed to hot temperatures as the expedition scientists found. (b) a little over 103,000 years ago, a large fire is known to have occurred in northern canada. (c) strong evidence exists that as early as 70,000 years ago, homo sapiens around the world relied heavily on fire to cook animals. (d) in the same expedition and in roughly the same layer of excavation, scientists found rudimentary wood cutting and hunting tools used by early humans.

Explain the source of radioactivity in uranium in earth’s crust by which it produces nuclear radiation