单选题 Under the guidance of their teacher, the pupils are building a model boat ______ by steam:

【正确答案】 C
【答案解析】propel推进，推动；tow(用绳索或链子)拖，拉；toss扔，抛，扬起，(使)颠簸，掷钱币(决定某事)；press按，压。句意：在老师的指导下，学生们在造一艘蒸汽模型船。