Researchers at one point in time assess and compare the performance of different age groups on the sat. the procedure used in this research best illustrates:

cross-sectional

Explanation:

cross-sectional study is a kind of study which investigate variables through analyzed the data collected in one specific time for a population.  In this study, sample of participants are the same in all variables except one.

in the mentioned research, changing variable is age.

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.

d

explanation:

it establishes america’s basic laws and fundamentals to its citizens.