independent institutions of higher education (that) charge tuition and fees of under $8,000 (are)more than three times as many as those charging (等同于that charge) over $16,000。 这才能说是比较2类学校,但是没有be动词。。。谁敢说这种句子ets会说它对。。。 正解: 主从主语相同,省略,charge留下与前对应。(非必须,但优于e charging)