In response to the soviet union’s invasion of afghanistan, the united statesratified the salt ii treaty. boycotted the 1980 summer olympics. increased grain shipments to afghanistan. stopped sending support to afghanistan.

The correct answer is: "boycotted the 1980 Summer Olympics. "

The 1980 Summer Olympic Games took place in Moscow, the capital of the Soviet Union at that time. In this edition of the Olympiad only 80 countries participated, the smallest number for 25 years.

The US, during the presidency of Jimmy Carter, plus other 66 countries under its influence and members of the capitalist Cold War block, decided to boycott the games as a punishment to the Soviet Union after the invasion of Afganistan, that had started in December of 1979.