题目

阅读下面短文，从短文后各题所给的四个选项(A、B、C、和D)中，选出可以填入空白处的最佳选项。 Lately I've been concerned about the environment. Last weekend I participated in the great Canadian shoreline 1. On that day, my mother and I arrived at 9:30 a.m. More than fifty people 2 and all the volunteers were divided into groups. The shoreline has four sections with the last two being the most 3 terrain(地形)—steep hills, lots of trees and rocks. We chose section four and after a brief speech from the organizer, we set off. We saw a lot of waste along the我国含沙量最大的河流是（ ）A．长江B．黄河C．松花江D．珠江