Christine uses an electric can opener to open cans of dog food. Her dog starts to salivate just at the sound of the electric can opener in anticipation of the food. According to the principles of classical conditioning, the electric can opener has become an effective for the dog.

conditioned stimulus is the correct answer.

Explanation:

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.

portugal is the westernmost country in europe.