Is it a, b, c, d ???

I believe that it is D.

Explanation:

If ice caps are melting, and polar bears use the ice flows to get their food, then the polar bears can't use the ice to get food. so, the polar bears most likely are expanding their diets to adapt to their surroundings. So, polar bears are probably moving off the sea ice and eating other foods.

d bonding propertys

explanation:

carbon can form so many different compounds not just with oxygen

c. earths continental crust is thicker than its lithosphere.

because, the lithosphere is the outermost layer of the earth/ 100 km thick and is defined by its machanical properties.the lithosphere contains oceanic and continental crust that varies in age and thickness across locations and geologic time. the lithosphere is the coolest layer of the earth in terms of temperature. the term lithosphere should not be confused with the use of "geosphere" which is used to indicate all of earth systems, including the atmosphere, hydrosphere   and biosphere. the surface of the earth can be divided into the continental crust and the oceanic crust.   the continental crust is made mostly of granite while the oceanic crust is made of basalt. the average thickness of the continental crust is 25 miles and the average thickness of the oceanic crust is 5 miles.   three types of rock, igneous, sedimentary, and metamorphic, make up the surface of the earth. that's why 3 option is preferable.