As children move beyond two-word utterances, they begin using plural and possessive nouns, appropriate verb endings, prepositions, articles, and various forms of the verb âto be.â this is evidence that children:

know morphological rules.

Explanation:

Morphological rules -

Morphology simply refers to the study of words , formation of words and the link between the words , is referred to as Morphology.  

Morphological rules consists of the rules , which are responsible to make a proper word and sentence.  

As the child grows , he tries to adapt to the morphological rules in order to learn new words and make sentences .  

Hence, from the given scenario of the question,  

The correct term is Morphological rules .

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.

a would be the answer