Answer:
James writes, "[Plough snails] can detect even the tiniest amount of dead animal particles in the water" (20).
Step-by-step explanation:
Writers should be careful when quoting a source. Any change that the writer made to the words being quoted should be apparent to the reader. The correct answer is the only sentence that correctly quotes the book. The quoted sentence begins with "They" in the passage, but the writer placed brackets around the change to show the reader that the wording was altered for clarity.