The conclusion that can be drawn from the excerpt is: "If they are well planned, they can protect the shore from erosion while minimizing damage to important habitats for plants and animals." Therefore, the option "If they are well planned, they can replace sand that has been washed away" is not accurate, and the options "If they are well planned, they will most likely be too expensive," and "If they are not well planned, they can damage other structures" are not supported by the information provided in the excerpt. The correct answer is: "If they are not well planned, they can damage places with sea life."