Answer:
C: "because."
Step-by-step explanation:
The word or phrase in the passage that suggests a cause-and-effect relationship is "because." In the sentence "They may have been able to farm, but there was no need for it because enough food already grew in the area to feed them," the word "because" introduces a reason that explains why the early people did not need to farm. Therefore, the correct answer is option C: "because."