What is the best definition of a labor union?

a. a group of employers who come together to advance their economic interests
b. a group of workers who come together to advance their common interests
c. a group of masters who come together to offer apprenticeships to skilled workers
d. a group of workers who come together to offer apprenticeships to skilled workers

can you explain it better

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.