COMB in N-COUNT (美国英语用法,用于first, second等词后构成名词)表示“…年级学生”-grader combines with words such as 'first' and 'second' to form nouns which refer to a child or young person who is in a particular grade in the American education system. (美国英语用法,用于first, second等词后构成名词)表示“…年级学生”