A-A+
What does the passage mainly discuss？A．How can
问题详情
What does the passage mainly discuss？
A．How canals are constructed.
B．Common types of canal boats and barges.
C．The world" s largest canals.
D．How canals are used and classified.请帮忙给出正确答案和分析，谢谢！
参考答案
正确答案：D
解析：通读全文不难发现，每段第一句即为段落主题句，第一段讲什么是canal，第二、三段讲的canal不同分类及其作用，因而本题应该选D。
