1.(the boy) (was taking) to school (by his father) when I (saw) him
Ta thấy : was taking sai nên ta sửa lại thành was being taken
(dựa vào verd: Chủ ngữ +was/were+being+V-pp)
2.the exercise (was) (such) difficult (that) we(couldn't do) it
Ta thấy : such sai nên ta sửa lại thành so
(dựa vào verd: Chủ ngữ +V+so+adj+that+....)