Answer: a). Spain
b). none
c). 2.4
Explanation: a). Absolute advantage occurs when a country produces more of a good than the other country. In this case, Spain produces 50 units of Tractors while, Bolivia produces only 30 units of Tractors. Thus, Since Spain is producing more it has an absolute advantage in Tractors.
b). Both the countries are producing equal units of Cotton. Thus, we can say that none of them has an absolute advantage in cotton production.
c. Opportunity cost is the cost of the lost alternative. When Spain produces Tractors it is sacrificing production of Cotton. So, opportunity cost on 1 unit of Tractor will be,

Thus, 2.4 units of cotton which is given up is the opportunity cost of Spain for producing 1 unit of Tractor.
Hello!
You forgot the alternatives!
incentives
<span>margin </span>
<span>markets </span>
<span>scarcity
</span>
The term that is most closely related to trade-off, from the list above, is: scarcity. Scarcity is the condition that moves the trade-offs, it determines the quantity of each product you need or have. So, for example, if you need a product that you don't have enough and another that you have in excess, you can exchange it with someone that have interest in your product and has the one that you need.
Hugs!
Because how do you know whether or not to accept the position. How do you know if it’s the right job for you? Or, what if you have to choose between two appealing offers? Will you feel comfortable with the people you work with?