Answer: d. export ban
Step-by-step explanation:
An Export Ban as the term implies refers to restrictions on the sale of a good to another country or set of countries.
In 1975, OPEC in a bid to drive up prices as well as punish countries it viewed as sympathetic to Israel, refused to supply the US and it's Allies with Oil thus reducing supply in the market. This had the effect of driving up oil prices and accomplishing their goals.
It had the effect of encouraging the US to implement an export ban so that domestic production in the US could be ramped up to take care of the population should OPEC ever threaten them again.