Why is the correct answer B?

Hello @cjahangiri, Let's break down the argument. Critics: building on land that is under 5 meters of water will reduce the size of the dolphin habitat. Premise: Dolphins never enter water that is more than 30 meters deep. Premise: The dolphin habitat is located between the shore and water that is over 30 meters deep. Conclusion: The critics are mistaken, the building site will not reduce the habitat size. What extra piece of information will prove to us that the critics are mistaken? B gives us a logical completion of the argument. If dolphins do not inhabit water that is less than 10 meters deep, then the 5 meter section was already not a part of the dolphin habitat. Therefore, building sites on this part will not affect the habitat.

I am confused. How did they come up with 10 meters? I only see the reference to 5 meters?

Hello, where did the 10 meters come from?