"which general research design permits determination of cause and effect relationships among variables? "

The field experiment is a general research design that permits determination of cause and effect relationships among variables. The field experiment is an experiment that takes place in a naturalistic setting such as home, school, or a playground. It is a scientific method that uses  objective and replicable methods to gather data for the purpose of testing a theory or hypothesis.

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.