Critics of a plan to create new building sites from land that currently lies under only 5 meters of water claim that ...

on September 24 at 11:15PM

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.