Answer:
Settlers
Explanation:
The indirect object refers to to someone or something affected by the action of a transitive verb (usually as a recipient), but is not the main object (e.g. her in "tell her the story").
The rest of the choices are incorrect because American Indians is the subject of the sentence, the word corner is not included in the sentence, and how to plant is the direct object, which is a noun phrase that designates a person or thing that is the recipient of the action of a transitive verb. (e.g. the cat in "Maria touched the cat").
