Question

As a result of Nixon’s support of Israel in the Yom Kippur War *
Nixon chose to withdraw from Vietnam
OPEC instituted an oil embargo
The U.S. was forced to fight a war in the Middle East in the 1970s
The president began to develop a space-based laser system

Answer 1

As a result of the support of the war effort in OPEC instituted an oil embargo

OPEC instituted an oil embargo

Explanation:

The oil embargo happened because the nations that constituted OPEC warned the nation that supporting Israel in the war would lead to that.

The US had openly supported the Israel war effort and thus all the oil rich nations of the OPEC including Saudi Arabia, UAE and Oman had signed the embargo.

BY the virtue of this, the export of oil to US was stopped.