单选题 Fine freshwater pearls are found in the main stream and the {{U}}tributaries{{/U}} of the Mississippi River.
  • A. banks
  • B. deltas
  • C. branches
  • D. currents
【正确答案】 C
【答案解析】[解析] tributary意思是“支流”，与branch(分支，支流)意思相近。bank银行，岸；delta(河流的)三角洲；current气流，水流，电流。