The night before a midterm exam, you decide to go to the movies instead of studying for the exam. You score 60 percent on your exam. If you had studied the night before, you'd have scored 70 percent. What was the opportunity cost of your evening at the movies?

10% of exam score

Explanation:

Opportunity Cost is the cost of next best alternative, foregone (sacrifised)  while making a choice.

Example : If a person has option to have an apple or an orange, & choses to have apple. The opportunity cost of having an apple is the sacrifised orange.

Given : A night before mid time exam, spent while watching movies - later lead to fall in exam grade from 70 % to 60%

The opportunity cost of movies watched, is the sacrifised grade of exam, which would have gotten, if the time would have spent in studying. The corresponding grade lost = 70% grade achievable - 60% grade achieved. Hence, the opportunity cost = 10% of exam score.

ans.

heterothermic organisms include those organisms that can switch between homeothermic (having body temperature higher than environment) and poikilothermic (having variation in internal body temperature) strategies.

some migratory birds show heterothermy as they decrease their metabolic rate during cold nights to keep their body temperature low. drop in metabolic rate allows increase in production efficiency of birds that reduces the internal body temperature to make it equal to external cold temperature during cold nights.

thus, the correct answer is 'birds allow their temperature drop in order to increase their production efficiency.'

answer(b) revenue account which increases;