They are used by workers to produce goods and services similar to the way physical capital is used.
The Cuban Missile Crisis was effectively ended when the 1. Soviet Union agreed to withdraw weapons from Cuba. The United States had set up the Acorn Line, a hypothetical line in the Caribbean Sea, which Kennedy stated no Soviet submarines or ships were allowed to pass. Fortunately, the Soviet Union withdrew missiles mainly because the United States also agreed to withdraw its missiles from Turkey.
The answer for this question is (d)
