What spheres are formed by remains of living things with a black hard surface

Biosphere

Explanation:

The spheres that are formed by remains of living things with a black hard surface are known as BIOSPHERE.

This is because the Biosphere is a combination of both living organisms (biotic) and nonliving organisms (abiotic) to form an ecosystem. It also includes the lithosphere, atmosphere, and hydrosphere.

Hence, the remains of living things are part of the biotic part, while a black hard surface is a form of abiotic part of the biosphere.

the correct answer is modern american cars are not available due to trade restrictions.

trade between cuba and the united states have serious restrictions. the u.s. imposed an economic embargo on cuba, that among other things means that modern american cars are not available due to trade restrictions.

in response to some governmental actions of the authorities from cuba, president john f. kennedy proclaimed an embargo on trade between both countries in february 1962. the trade embargo remains active until this day and was implemented directly by the departments of commerce and the department of treasury.

in president trump’s administration, there is a national security presidential memorandum that "strengthens the policy of the u. s.", affecting trade with cuba.