10. Building that railway was very difficult and involved _____ ten tunnels.
A. dig
B. throwing
C. to have thrown
D. having thrown
出自:河北建筑工程学院-建筑工程技术(专科)-大学英语1

完成拼图验证

按住下方滑块,将拼图拖到缺口处后松开。

拼图背景,将小拼图拖到缺口处
向右拖动滑块