Which of the following is an example of an essential question? How many gallons of water are in the Pacific Ocean?
Did the ancient Romans eat pasta?
What is happiness?
How does photosynthesis produce oxygen?

The question "What is happiness?" is an essential question.

Explanation:

Essential questions are questions that are, well, essential. Essential questions are not supposed to be easy to answer, are often classified as "deep", and are usually going to provoke thought.

While the question "Did the ancient Romans eat pasta?" does seem essential, it is easy to answer, which does not make it an essential question. The question "How many gallons of water are in the Pacific Ocean?" and "How does photosynthesis produce oxygen?" could be classified as essential questions, but they are not essential questions as they are trivial questions (trivial questions are of little importance and usually look like like "How tall is Michael Jordan?" and "How many feet are in a acre?").

its c i just did it on apex