Which statement best compares the laws of supply and demand?

After a little searching I found the answer choices to your question. They are:

1) The two economic laws exist in theory. They have no relation to economics in the real world.

2) The two economic laws exist in theory. They work in practice, but real-world factors can have an effect.

3) The two economic laws work in practice. They apply to real-world economics eighty percent of the time.

4) The two economic laws work in practice. They prove to be true in the real world one hundred percent of the time.

The answer to your question is 4.