question: Why were the lands in the region the Sumerian people settled fertile ?
answer: silt deposited by the Tigris and the Euphrates rivers
turker_answer: Silt deposited by the Tigris and the Euphrates rivers made the Sumerian lands fertile .
rule-based: The lands in the region the Sumerian people were settled fertile because of silt deposited by the Tigris and the Euphrates rivers .