Circle the bracketed words or phrase in each sentence that needs correcting and then correct it

circle the bracketed words or phrase in each sentence that needs correcting and then correct it
1(do) you( know) the school (where) he( used) to study at
2 it (took)the (director ) two hours (explaining) the new plan (to) us
3 this lesson (is) (such) long (that) i (have written) it for 30 minutes
4 (a large number of students) in this school (speaks) french (fairly fluenty)
5 we can (prevent) floods (by) (preservation) (the forests)