找出错误项并在横线上改错

找出错误项并在横线上改错1.I will return the book back in two days.-----a.will b.return c.back d.in the days 2.Todays we'll climb a mountain which is 800 meters over sea level.-----a.climb b.is c.800 meters d.over3.I don't know when will he come back .-----a.don't know b.when c.will he d. come back 4.I think he isn't a very hard-working student.-----a.think he isn't b. a c.very d.hard-working