What caused relations to deteriorate between the united states and the soviet union in 1979?

The answer is that The Soviet Union invaded Afghanistan to help its Communist government.

Although US was involved, it does not invaded the nation instead was offering help with the consent of Afghanistan government.

In 1979, the US helped the opposition faction in the Afghanistan to launch an armed uprising in order to overthrow the pro-Soviet government. The Soviet Union, worrying that it would lose control over Afghanistan, send troops and invaded it immediately.

As Afghanistan was one of the major oil supplier to US, once the region fell into USSR control, the oil supply would be greatly affected, thus it was resentful towards USSR's action of the invasion, causing their relations to deteriorate.

Therefore The Soviet Union invaded Afghanistan to help its Communist government is the answer.

Hope it helps!

i thing that the best option is a.they feared it would cause a second economic collapse.

one of the most negatives aspects of the new deal was that it upset the balanced federal budget and led to a huge deficit for the nation while at the same time failed to end increasing unemployment. roosevelt's program, based on keynesian theories of economics, called for massive government spending to stimulate the economy. as he   failed to do this with large tax increases; large sums of money were borrowed to fund new deal programs. when the economy showed some improvement, roosevelt was concerned about inflation, and ordered cuts in government spending. unfortunately, he did so at a time when the new social security tax had cut people's disposable income. businesses were too afraid of spending, and the economy in 1937 was in worse shape than in 1929. at the end of that year, two million people were unemployed.