Studies of deaf children who are not exposed to a formal sign language indicate that the children spontaneously produce their own signs, called home signs, which emerge in development at the times of typical language milestones. however, the children relying on home signs are limited in that

I believe the answer is: they do not advance beyond the telegraphic phase of language

During the telegraphic phase of language, we would learn to differentiate longer and shorter words in order to determine which one is more efficient in the current context. Deaf people tend to unable to pass this since they never heard how long and short sentence sounds like.

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.