21.【2020 •贵州省安顺市】With the improvement in transportation, students in some small villages no longer go on ropeways ______ rivers to schools.
A. to cross B. crossing C. crossed
【答案】A
【解析】句意：随着交通的改善，一些小村庄的学生不再走索道过河上学。考查非谓语动词。to cross动词不定式形式；crossing动名词形式；crossed动词过去分词形式。根据空前的go on ropeways结合选项动词cross可知，此处是动词不定式表目的状语，走索道过河上学go on ropeways to cross rivers to schools符合句意。故选A。